COG8-congenital disorder of glycosylation

👪

Inheritance

1

Autosomal recessive HP:0000007

Biallelic COG8 variants underlie the disorder. Homozygous and compound-heterozygous genotypes are reported; the parents in the 2017 compound-heterozygous family carried the respective variants. When both parents are carriers, each pregnancy has a 25% affected, 50% carrier and 25% noncarrier probability.

Autosomal recessive inheritance

Show evidence (3 references)

PMID:28619360 SUPPORT Human Clinical

"The parents were heterozygous carriers of each variant."

Segregation of the two truncating COG8 variants to unaffected heterozygous parents establishes autosomal recessive inheritance.

PMID:17220172 SUPPORT Human Clinical

"Here, we describe a patient with a mild form of a congenital disorder of glycosylation type II (CDG-II), which is caused by a homozygous nonsense mutation in the hCOG8 gene."

A homozygous nonsense COG8 variant in an affected patient supports a biallelic, recessive disease mechanism.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/ SUPPORT INDIRECT REVIEW SYNTHESIS Other

"At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic ... carrier ... and a 25% chance of being unaffected and not a carrier."

Historical group-level autosomal-recessive counseling applies when both parents carry a disease-causing COG8 allele.

?

Discussions and Knowledge Gaps

3

Does the reduced glycosaminoglycan modification of proteoglycans seen in COG-subunit knock-out cell lines occur in COG8-CDG patient tissue, and does it contribute to the skeletal and connective-tissue features?

KNOWLEDGE GAP cog8_proteoglycan_gag_in_patient_tissue

Attached to

experimental_models#COG8-knockout HEK293T proteoglycan model

Engineered COG8-knockout HEK293T cells have altered proteoglycan synthesis readouts, but their contribution to human COG8-CDG manifestations remains untested in the cited studies. Altered turnover was proposed rather than kinetically measured.

Show evidence (1 reference)

PMID:34053170 SUPPORT In Vitro

"In light of the important roles PGs play in animal development, the effects KO of individual COG subunits have on GAG synthesis could explain the variable severity of COG associated CDGs."

The authors state the hypothesis this gap would test, and frame it as a possible rather than established explanation.

What determines the clinical severity range in COG8-CDG, and how do residual protein, complex assembly and tissue context contribute?

KNOWLEDGE GAP cog8_severity_range_with_clustered_truncating_alleles

Attached to

pathophysiology#Abnormal N-glycan sialylation genetic#COG8 pathogenic variants

Residual truncated protein and biochemical sialylation defects differ between patient lines. A biochemically mild sialylation defect can accompany substantial neurological disease. The small case series cannot establish a genotype-severity model; the reported exon 5 clustering is not universal.

Show evidence (2 references)

PMID:28619360 SUPPORT Human Clinical

"Compared with the previous two reported cases, our patient showed relatively mild psychomotor retardation without a seizure history."

Documents the severity difference between reported patients that this gap concerns.

PMID:17220172 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Mass spectrometric analysis of the N- and O-glycan structures identified a mild sialylation deficiency."

Biochemically mild result does not imply absence of major neurological disability.

Which COG8-dependent trafficking and glycosylation defects cause the specific neurological, hepatic and coagulation manifestations?

KNOWLEDGE GAP cog8_glycan_to_organ_mechanisms

Attached to

pathophysiology#Abnormal N-glycan sialylation pathophysiology#Abnormal O-glycan sialylation

Cellular complementation establishes COG8 dependence for trafficking and glycan readouts, but specific substrate-to-organ causal chains have not been established in these studies. Clinical edges therefore retain unknown intermediates.

Show evidence (1 reference)

PMID:23865579 SUPPORT DIRECT BACKGROUND Other

"Yet, the connection between COG function, its complex integrity and CDG pathology remains largely unknown."

The mechanistic study states the unresolved connection to clinical pathology.

⚙

Pathophysiology

10

Biallelic COG8 dysfunction

Biallelic COG8 variants impair function of a lobe B component of the conserved oligomeric Golgi complex. Published genotypes include nonsense, frameshift and splice-altering alleles. Their cellular effects vary: absence of detectable COG8 and residual truncated protein have both been reported.

COG8 hgnc:18623

Experimental models

COG8-knockout HEK293T proteoglycan model CELL LINE

Downstream

Reduced COG8 protein abundance

Disrupted COG complex assembly

Global Developmental Delay Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Hypotonia Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Failure to Thrive Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Seizures Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Microcephaly Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Cerebellar Atrophy Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Elevated Serum Transaminases Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Talipes Equinovarus Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Dandy-Walker Malformation Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Arthrogryposis Multiplex Congenita Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Facial Dysmorphism Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Increased Nuchal Translucency Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Developmental regression Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Encephalopathy Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Esotropia Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Ataxia Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Action myoclonus Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Oculomotor apraxia Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Absent Achilles reflex Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Foot dorsiflexor weakness Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Brainstem atrophy Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Short stature Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Abnormality of coagulation Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Bruising susceptibility Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Elevated creatine kinase Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Recurrent fever Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.

Reduced protein C activity Clinical association in the reported COG8-CDG patient; tissue intermediates remain unresolved.

Reduced protein S activity Clinical association in the reported COG8-CDG patient; tissue intermediates remain unresolved.

Sandal gap Clinical association in the reported COG8-CDG patient; tissue intermediates remain unresolved.

Clinodactyly of the 3rd toe Clinical association in the reported COG8-CDG patient; tissue intermediates remain unresolved.

Clinodactyly of the 4th toe Clinical association in the reported COG8-CDG patient; tissue intermediates remain unresolved.

Show evidence (1 reference)

PMID:17331980 SUPPORT Human Clinical

"We describe a new Type II congenital disorder of glycosylation (CDG-II) caused by mutations in the conserved oligomeric Golgi (COG) complex gene, COG8."

Establishes COG8 as the causal gene.

Reduced COG8 protein abundance

COG8 was undetectable in the compound-heterozygous patient fibroblasts reported by Kranz et al. In the p.Tyr537Ter patient, a truncated protein remained detectable at about one quarter of control immunoreactivity. These are genotype-specific fibroblast measurements, not proof of complete absence in all tissues.

Experimental models

COG8-deficient CDG patient fibroblasts with lentiviral complementation PRIMARY CELL CULTURE The patient-derived line directly models the undetectable COG8 protein reported for this genotype.

Show evidence (2 references)

PMID:17331980 SUPPORT DIRECT PRIMARY RESULT In Vitro

"Patient fibroblasts completely lacked COG8 protein and had reduced levels and/or mislocalization of several other COG proteins."

Undetectable protein in this particular patient line.

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT In Vitro

"Moreover, compared with control, only 25% of the immunoreactivity was recovered, suggesting that the transcript or the truncated Cog8 protein is unstable"

Residual truncated protein in the p.Tyr537Ter line limits a universal null-protein claim.

Disrupted COG complex assembly

The p.Tyr537Ter truncation disrupts the COG1-COG8 interaction and intact complex assembly. Smaller subcomplexes remain. Secondary COG1 reduction is not uniform absence: COG1 remained weakly Golgi-localized in the p.Tyr537Ter patient, whereas it was not detected at the Golgi in the other patient line used in the 2013 study.

Downstream

Impaired Golgi SNARE complex assembly COG8 deficiency disrupts complex integrity and SNARE assembly; the precise intermediate interactions are incompletely resolved.

Delayed Golgi-to-ER retrograde transport

Impaired endosome-to-Golgi transport

Altered Golgi glycosylation enzyme localization

Reduced beta1,4-galactosyltransferase abundance

Abnormal N-glycan sialylation The biochemical link to COG8 dysfunction is established; the enzyme-specific contributions remain unresolved.

Abnormal O-glycan sialylation

Show evidence (3 references)

PMID:17220172 SUPPORT DIRECT PRIMARY RESULT In Vitro

"As a result, Cog1 deficiency accompanies the Cog8 deficiency, preventing assembly of the intact, stable complex and resulting in the appearance of smaller subcomplexes."

The interaction and fractionation studies identify a defect in complex integrity.

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT In Vitro

"Although weaker in immunofluorescence signal, as expected from the western blot analysis, the Cog1 subunit was associated with the Golgi in both the patient and control fibroblasts"

Retained localization in the p.Tyr537Ter patient prevents equating reduced COG1 abundance with loss from the Golgi in every genotype.

PMID:23865579 SUPPORT DIRECT PRIMARY RESULT In Vitro

"In CDG-derived Cog8-deficient fibroblasts, Cog1 was not detected in the Golgi"

Contrasting result in the patient line studied by Laufman et al.

Impaired Golgi SNARE complex assembly

Assembly of the Stx5-GS28-Ykt6-GS15 and Stx6-Stx16-Vti1a-VAMP4 complexes is reduced in COG8-depleted HeLa cells and the tested COG8-CDG fibroblasts. Protein abundance and localization differ between the systems; loss of complex assembly is not identical to loss of every SNARE protein.

SNARE complex assembly GO:0035493 ⚠ ABNORMAL

Experimental models

COG8 shRNA knockdown HeLa cells CELL LINE Reduced SNARE complex assembly is also observed in the tested patient fibroblasts.

Show evidence (2 references)

PMID:23865579 SUPPORT DIRECT PRIMARY RESULT In Vitro

"the interactions of Stx5 with either the v-SNARE GS15 or the t-SNAREs Ykt6 and GS28 were significantly reduced in both Cog8-deficient cell types."

NEM-stabilized immunoprecipitation detects reduced Stx5 complex assembly.

PMID:23865579 SUPPORT DIRECT PRIMARY RESULT In Vitro

"Despite the differences in the steady-state distributions of the SNARE proteins, the assembly of the Stx6 SNARE complex was impaired in both Cog8-deficient cell types."

Independent Stx6 complex assembly readout in both systems.

Delayed Golgi-to-ER retrograde transport

Patient fibroblasts exhibit delayed brefeldin A-induced redistribution of Golgi proteins. This pharmacological assay supports abnormal retrograde trafficking; it does not directly measure every physiological intra-Golgi transport step.

retrograde vesicle-mediated transport, Golgi to endoplasmic reticulum GO:0006890 ⚠ ABNORMAL

Experimental models

COG8-deficient CDG patient fibroblasts with lentiviral complementation PRIMARY CELL CULTURE

Show evidence (2 references)

PMID:17331980 SUPPORT DIRECT PRIMARY RESULT In Vitro

"Patient fibroblasts were deficient in sialylation of both N- and O-glycans, and also showed slower brefeldin A (BFA)-induced disruption of the Golgi matrix, reminiscent of COG7-deficient cells."

Patient-cell BFA redistribution result.

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT In Vitro

"In the patient's cells, however, the BFA-induced redistribution of Golgi mannosidase II was significantly delayed at all times investigated"

The p.Tyr537Ter line also has a delayed BFA response.

Impaired endosome-to-Golgi transport

COG8-depleted HeLa cells show delayed TGN38 antibody-uptake trafficking to the trans-Golgi network. Patient fibroblasts show altered endogenous TGN38/46 and CI-MPR distribution, supporting disturbed recycling but without the same kinetic assay in patient cells.

retrograde transport, endosome to Golgi GO:0042147 ⚠ ABNORMAL

Show evidence (2 references)

PMID:23865579 SUPPORT DIRECT PRIMARY RESULT In Vitro

"depletion of the Cog8 subunit substantially inhibited the transport of TGN38-HA to the TGN in HeLa cells."

Dynamic transport measurement is specific to the HeLa model.

PMID:23865579 SUPPORT DIRECT PRIMARY RESULT In Vitro

"Collectively, these results suggest that Cog8 deficiency in either HeLa cells or CDG-derived fibroblasts influences endosome-to-TGN retrograde transport."

Patient localization data support, but do not duplicate, the HeLa kinetic evidence.

Altered Golgi glycosylation enzyme localization

In COG8 siRNA-depleted HeLa cells, tested Golgi enzymes redistribute to vesicle-like structures and fragmented Golgi. This is not universal in patient fibroblasts: mannosidase II and beta1,4-galactosyltransferase retained perinuclear Golgi distribution in the p.Tyr537Ter patient. Effects depend on the protein, genotype and cell system.

Show evidence (2 references)

PMID:21421995 SUPPORT DIRECT PRIMARY RESULT In Vitro

"In all analyzed COG KD cells, MGAT1, MAN2A1 and ST6GAL1 proteins were found in multiple vesicle-like structures, as well as in large fragmented Golgi mini-stacks that were positive for the Golgi matrix protein GM130."

The tested panel included COG8-depleted HeLa cells.

url:https://oup.silverchair-cdn.com/article-minimal/654283 REFUTE DIRECT PRIMARY RESULT In Vitro

"Both enzymes appeared to exhibit a normal perinuclear Golgi distribution in the patient's cells"

Mannosidase II and beta1,4-galactosyltransferase localization counterexample in p.Tyr537Ter fibroblasts.

Reduced beta1,4-galactosyltransferase abundance

Beta1,4-galactosyltransferase abundance was reduced in the p.Tyr537Ter patient fibroblasts despite retained perinuclear localization. Abundance, localization and catalytic activity are distinct readouts; this experiment does not quantify a disease-wide enzyme deficiency.

Show evidence (1 reference)

PMID:17220172 SUPPORT DIRECT PRIMARY RESULT In Vitro

"Moreover, levels of beta1,4-galactosytransferase were significantly reduced."

Reduced enzyme abundance in the patient-cell study.

Abnormal N-glycan sialylation

Serum N-glycans and transferrin show incomplete terminal sialylation, with biochemical severity varying between cases. The markedly impaired addition of subsequent sialic acids described by Kranz et al. is not an invariant pattern in all genotypes. Acute COG8 knockdown in HeLa cells instead produced a minor increase in total cellular N-glycan sialylation.

protein N-linked glycosylation GO:0006487 ⚠ ABNORMAL

Experimental models

COG8-deficient CDG patient fibroblasts with lentiviral complementation PRIMARY CELL CULTURE

COG8 siRNA-depleted HeLa cells CELL LINE

Downstream

Type II Transferrin Isoelectric Focusing Pattern Incomplete sialylation of serum transferrin gives the CDG type II isoelectric focusing profile.

Show evidence (3 references)

PMID:17331980 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Analysis of serum transferrin and total serum N-glycans showed normal addition of one sialic acid, but severe deficiency in subsequent sialylation of mostly normal N-glycans."

Serum finding in one patient.

PMID:17220172 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Mass spectrometric analysis of the N- and O-glycan structures identified a mild sialylation deficiency."

Biochemically mild result does not imply absence of major neurological disability.

PMID:21421995 REFUTE DIRECT PRIMARY RESULT In Vitro

"Surprisingly, the data also show a minor increase in sialylation in the N-glycans of COG6- and COG8-deficient cells."

Total-cell HeLa N-glycans differ from patient serum findings; the model does not reproduce this readout.

Abnormal O-glycan sialylation

Patient serum O-glycan analysis, ApoC-III isoelectric focusing and fibroblast lectin assays identify an O-glycosylation defect. In the p.Tyr537Ter patient, wild-type COG8 complementation reduced abnormal PNA staining. This is cellular rescue, not a demonstrated clinical gene therapy.

protein O-linked glycosylation GO:0006493 ⚠ ABNORMAL

Experimental models

COG8-deficient CDG patient fibroblasts with lentiviral complementation PRIMARY CELL CULTURE

Show evidence (2 references)

PMID:17220172 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Mass spectrometric analysis of the N- and O-glycan structures identified a mild sialylation deficiency."

Serum glycan analysis confirms the O-glycan component.

PMID:17220172 SUPPORT DIRECT PRIMARY RESULT In Vitro

"The defects in O-glycosylation could be fully restored by transfecting the patient's fibroblasts with full-length Cog8."

Complementation supports a COG8-dependent cellular phenotype.

✶

Histopathology

1

Interface hepatitis with mild lobular activity

Liver biopsy in the 2017 Korean patient showed interface hepatitis with mild lobular activity. This single observation is not a COG8-specific diagnostic pattern.

Show evidence (1 reference)

PMID:28619360 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"A liver biopsy of the patient showed only interface hepatitis with mild lobular activity, and brain magnetic resonance imaging revealed cerebellar atrophy."

Biopsy morphology in one Korean patient; this does not establish a specific inflammatory mechanism or a population frequency.

⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

●

Phenotypes

32

Blood 4

Abnormality of coagulation HP:0001928

Show evidence (1 reference)

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"During some other episodes, she presented spontaneous hematomas, coincident with alteration of the coagulation factors and a decrease in the prothrombin time, together with increased levels of transaminases and of creatine kinase."

Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.

Bruising susceptibility HP:0000978

Show evidence (1 reference)

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"During some other episodes, she presented spontaneous hematomas, coincident with alteration of the coagulation factors and a decrease in the prothrombin time, together with increased levels of transaminases and of creatine kinase."

Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.

Reduced protein C activity HP:0005543

Show evidence (1 reference)

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Because of her occasional coagulation problems, bleeding or thrombosis, and the fluctuation of the coagulation parameters throughout development (protein C and protein S deficiency, decreased prothrombin time and coagulation factors), a wide study for"

Direct clinical observation in one patient; no population frequency or independent causal mechanism is established.

Reduced protein S activity HP:0004855

Show evidence (1 reference)

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Because of her occasional coagulation problems, bleeding or thrombosis, and the fluctuation of the coagulation parameters throughout development (protein C and protein S deficiency, decreased prothrombin time and coagulation factors), a wide study for"

Direct clinical observation in one patient; no population frequency or independent causal mechanism is established.

Eye 2

Esotropia HP:0000565

Show evidence (2 references)

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Although the neonatal period and early infancy were normal, at the age of 6 months, she presented with an acute encephalopathy and loss of psychomotor abilities, hypotonia, alternating esotropia, pseudo-ptosis and mental retardation."

Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/ SUPPORT DIRECT REVIEW SYNTHESIS Other

"Two affected infants with severe developmental delay, hypotonia, seizures, esotropia, failure to thrive, and progressive microcephaly were reported"

COG8-specific paragraph of the retired GeneReviews overview; supports association, not a frequency estimate.

Oculomotor apraxia HP:0000657

Show evidence (1 reference)

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"A detailed clinical evaluation now revealed an oculomotor apraxia with dysinergia oculocephalica, in addition to the pseudo-ptosis and alternating esotropia; fundoscopy was normal."

Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.

Head and Neck 4

Microcephaly HP:0000252

Reported in a patient (PMID:28619360).

Show evidence (2 references)

PMID:28619360 SUPPORT Human Clinical

"Here, we describe an 8-year-old Korean boy with psychomotor retardation, hypotonia, failure to thrive, elevated serum liver enzymes, microcephaly, and talipes equinovarus."

Reports microcephaly.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/ SUPPORT DIRECT REVIEW SYNTHESIS Other

"Two affected infants with severe developmental delay, hypotonia, seizures, esotropia, failure to thrive, and progressive microcephaly were reported"

COG8-specific paragraph of the retired GeneReviews overview; supports association, not a frequency estimate.

Dandy-Walker Malformation HP:0001305

Reported only in the antenatally ascertained patient (PMID:30690882), whose authors present it as an expansion of the COG8-CDG phenotype.

Show evidence (1 reference)

PMID:30690882 SUPPORT Human Clinical

"We present the first case of antenatally diagnosed COG8-CDG with facial dysmorphism and additional features such as Dandy-Walker malformation and arthrogryposis multiplex congenita, thus expanding the phenotype of this rare disorder."

Reports Dandy-Walker malformation.

Facial Dysmorphism Abnormal facial shape HP:0001999

Facial dysmorphism was reported in the antenatal case; the retrieved abstract does not specify individual facial features.

Show evidence (1 reference)

PMID:30690882 SUPPORT Human Clinical

"We present the first case of antenatally diagnosed COG8-CDG with facial dysmorphism and additional features such as Dandy-Walker malformation and arthrogryposis multiplex congenita, thus expanding the phenotype of this rare disorder."

Reports facial dysmorphism.

Increased Nuchal Translucency HP:0010880

Reported in a patient (PMID:30690882).

Show evidence (1 reference)

PMID:30690882 SUPPORT Human Clinical

"An association between antenatally increased nuchal translucency and COG8-CDG is also established, which would alert clinicians to its diagnosis early in gestation."

Reports the antenatal nuchal translucency finding.

Limbs 6

Talipes Equinovarus HP:0001762

Reported in a patient (PMID:28619360).

Show evidence (1 reference)

PMID:28619360 SUPPORT Human Clinical

"Here, we describe an 8-year-old Korean boy with psychomotor retardation, hypotonia, failure to thrive, elevated serum liver enzymes, microcephaly, and talipes equinovarus."

Reports talipes equinovarus.

Absent Achilles reflex HP:0003438

Show evidence (1 reference)

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"She has symptoms of neuropathy in the lower limbs because she walks with ataxia and foot drop; she has abolished achilles tendon reflexes."

Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.

Foot dorsiflexor weakness HP:0009027

Show evidence (1 reference)

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"She has symptoms of neuropathy in the lower limbs because she walks with ataxia and foot drop; she has abolished achilles tendon reflexes."

Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.

Sandal gap HP:0001852

Show evidence (1 reference)

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Minor dysmorphic features: small feet, wide space between the first and second toes and clinodactyly of the third and fourth toes can be observed."

Direct clinical observation in one patient; no population frequency or independent causal mechanism is established.

Clinodactyly of the 3rd toe HP:0008115

Show evidence (1 reference)

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Minor dysmorphic features: small feet, wide space between the first and second toes and clinodactyly of the third and fourth toes can be observed."

Direct clinical observation in one patient; no population frequency or independent causal mechanism is established.

Clinodactyly of the 4th toe HP:0011918

Show evidence (1 reference)

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Minor dysmorphic features: small feet, wide space between the first and second toes and clinodactyly of the third and fourth toes can be observed."

Direct clinical observation in one patient; no population frequency or independent causal mechanism is established.

Metabolism 4

Elevated Serum Transaminases Elevated circulating hepatic transaminase concentration HP:0002910

Reported in a patient (PMID:28619360).

Show evidence (2 references)

PMID:28619360 SUPPORT Human Clinical

"Here, we describe an 8-year-old Korean boy with psychomotor retardation, hypotonia, failure to thrive, elevated serum liver enzymes, microcephaly, and talipes equinovarus."

Reports elevated serum liver enzymes.

PMID:28619360 SUPPORT Human Clinical

"A liver biopsy of the patient showed only interface hepatitis with mild lobular activity, and brain magnetic resonance imaging revealed cerebellar atrophy."

Characterises the hepatic involvement histologically as mild interface hepatitis.

Type II Transferrin Isoelectric Focusing Pattern Type II transferrin isoform profile HP:0012301

The diagnostic biochemical signature. Directly reported in PMID:28619360; the index report (PMID:17331980) describes the same defect at the level of serum transferrin and total serum N-glycans.

Show evidence (2 references)

PMID:28619360 SUPPORT Human Clinical

"The transferrin isoelectric focusing profiles in the patient showed a CDG type II pattern with increased disialo- and trisialo-transferrin."

Directly reports the CDG type II transferrin pattern.

PMID:17331980 SUPPORT Human Clinical

"Analysis of serum transferrin and total serum N-glycans showed normal addition of one sialic acid, but severe deficiency in subsequent sialylation of mostly normal N-glycans."

The index report characterises the same serum transferrin sialylation defect that produces the type II pattern.

Elevated creatine kinase Elevated circulating creatine kinase activity HP:0003236

Show evidence (1 reference)

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"During some other episodes, she presented spontaneous hematomas, coincident with alteration of the coagulation factors and a decrease in the prothrombin time, together with increased levels of transaminases and of creatine kinase."

Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.

Recurrent fever HP:0001954

Show evidence (1 reference)

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"During infancy, she exhibited PFAPA syndrome (periodic fever, aphthous stomatitis, pharyngitis and adenitis)"

Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.

Musculoskeletal 2

Hypotonia HP:0001252

Reported in a patient (PMID:28619360).

Show evidence (2 references)

PMID:28619360 SUPPORT Human Clinical

"Here, we describe an 8-year-old Korean boy with psychomotor retardation, hypotonia, failure to thrive, elevated serum liver enzymes, microcephaly, and talipes equinovarus."

Reports hypotonia among the presenting features.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/ SUPPORT DIRECT REVIEW SYNTHESIS Other

"Two affected infants with severe developmental delay, hypotonia, seizures, esotropia, failure to thrive, and progressive microcephaly were reported"

COG8-specific paragraph of the retired GeneReviews overview; supports association, not a frequency estimate.

Arthrogryposis Multiplex Congenita HP:0002804

Reported only in the antenatally ascertained patient (PMID:30690882).

Show evidence (1 reference)

PMID:30690882 SUPPORT Human Clinical

"We present the first case of antenatally diagnosed COG8-CDG with facial dysmorphism and additional features such as Dandy-Walker malformation and arthrogryposis multiplex congenita, thus expanding the phenotype of this rare disorder."

Reports arthrogryposis multiplex congenita.

Nervous System 8

Global Developmental Delay HP:0001263

Reported in the index patient (PMID:17331980) and in the third published patient (PMID:28619360). The small case series does not establish a population frequency.

Show evidence (2 references)

PMID:17331980 SUPPORT Human Clinical

"The patient has severe psychomotor retardation, seizures, failure to thrive and intolerance to wheat and dairy products."

Severe psychomotor retardation in the index COG8-CDG patient.

PMID:28619360 SUPPORT Human Clinical

"Compared with the previous two reported cases, our patient showed relatively mild psychomotor retardation without a seizure history."

A second patient with psychomotor retardation, explicitly milder than the earlier cases.

Seizures HP:0001250

Present in the index patient (PMID:17331980); explicitly absent in the patient of PMID:28619360. Not a constant feature.

Show evidence (3 references)

PMID:17331980 SUPPORT Human Clinical

"The patient has severe psychomotor retardation, seizures, failure to thrive and intolerance to wheat and dairy products."

Seizures in the index patient.

PMID:28619360 REFUTE Human Clinical

"Compared with the previous two reported cases, our patient showed relatively mild psychomotor retardation without a seizure history."

Cited against seizures being a constant feature: this patient had no seizure history.

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"She has not suffered further epileptic seizures other than the status convulsivus at 17 months and she does not need antiepileptic drugs."

Single-patient longitudinal course; not a general recommendation to withhold seizure treatment.

Cerebellar Atrophy HP:0001272

Documented by MRI in PMID:17220172 and PMID:28619360.

Show evidence (2 references)

PMID:28619360 SUPPORT Human Clinical

"A liver biopsy of the patient showed only interface hepatitis with mild lobular activity, and brain magnetic resonance imaging revealed cerebellar atrophy."

MRI-documented cerebellar atrophy.

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"At the age of 6 years, brain magnetic resonance imaging (MRI) showed cerebellar atrophy and slight brainstem atrophy"

Clinical MRI result in the p.Tyr537Ter patient.

Developmental regression HP:0002376

Show evidence (1 reference)

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Although the neonatal period and early infancy were normal, at the age of 6 months, she presented with an acute encephalopathy and loss of psychomotor abilities, hypotonia, alternating esotropia, pseudo-ptosis and mental retardation."

Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.

Encephalopathy HP:0001298

Show evidence (1 reference)

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Although the neonatal period and early infancy were normal, at the age of 6 months, she presented with an acute encephalopathy and loss of psychomotor abilities, hypotonia, alternating esotropia, pseudo-ptosis and mental retardation."

Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.

Ataxia HP:0001251

Show evidence (1 reference)

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"From the age of 7, her cerebellar ataxia has worsened."

Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.

Action myoclonus HP:0034360

Show evidence (1 reference)

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"She later developed a cerebellar syndrome with prominent ataxia and action myoclonus."

Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.

Brainstem atrophy Atrophy/Degeneration affecting the brainstem HP:0007366

Show evidence (1 reference)

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"At the age of 6 years, brain magnetic resonance imaging (MRI) showed cerebellar atrophy and slight brainstem atrophy"

Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.

Growth 2

Failure to Thrive HP:0001508

Reported in the index patient (PMID:17331980) and in the third published patient (PMID:28619360).

Show evidence (2 references)

PMID:17331980 SUPPORT Human Clinical

"The patient has severe psychomotor retardation, seizures, failure to thrive and intolerance to wheat and dairy products."

Failure to thrive in the index patient.

PMID:28619360 SUPPORT Human Clinical

"Here, we describe an 8-year-old Korean boy with psychomotor retardation, hypotonia, failure to thrive, elevated serum liver enzymes, microcephaly, and talipes equinovarus."

Failure to thrive in a second patient.

Short stature HP:0004322

Show evidence (1 reference)

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"The Cog8-defective patient suffers from cerebellar atrophy, mental and motor retardation, hypotonia, growth delay and short stature."

Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.

🧬

Genetic Associations

1

COG8 pathogenic variants (Causal)

Gene: COG8 hgnc:18623 relationship_type: CAUSATIVE

Show evidence (3 references)

PMID:17331980 SUPPORT Human Clinical

"We describe a new Type II congenital disorder of glycosylation (CDG-II) caused by mutations in the conserved oligomeric Golgi (COG) complex gene, COG8."

Establishes COG8 as the causal gene.

PMID:28619360 SUPPORT Human Clinical

"Targeted exome sequencing was performed to screen all CDG type II-related genes, and two novel frameshift mutations were found: c.171dupG (p.Leu58Alafs*29) and c.1656dupC (p.Ala553Argfs*15) in COG8."

Reports two further truncating COG8 alleles in a third patient.

PMID:17331980 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"The first, IVS3 + 1G > A, altered the conserved splicing site of intron 3, and the second deleted two nucleotides (1687-1688 del TT) in exon 5, truncating the last 47 amino acids."

Direct counterexample to a universal exon 5 location claim.

Variants (4)

c.1611C>G (p.Tyr537Ter) Pathogenic

single nucleotide variant

Genomic context: coding sequence

A homozygous nonsense change introducing a premature stop codon, leaving a Cog8 subunit that lacks its 76 C-terminal amino acids and so cannot bind Cog1.

Show evidence (2 references)

PMID:17220172 SUPPORT Human Clinical

"This leads to a premature stop codon resulting in a truncated Cog8 subunit lacking the 76 C-terminal amino acids."

Defines the allele and the precise extent of the C-terminal truncation.

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"We found a nonsense mutation (C to G) at position c.1611 in the ... COG8 ... cDNA, and this was confirmed by the genomic DNA sequence."

Original sequence nomenclature in the clinical report.

Homozygous exon 5 variant creating a new splice site Pathogenic

The 2019 report describes a homozygous exon 5 splice-creating variant with a truncating consequence. The retrieved abstract does not establish the RNA assay or quantify residual protein.

Show evidence (1 reference)

PMID:30690882 SUPPORT Human Clinical

"Trio whole exome sequencing revealed a novel homozygous variant in COG8, which creates a new splice site in exon 5 and protein truncation after 12 amino acids downstream to the newly generated splice site."

Defines the antenatally ascertained patient's allele.

IVS3+1G>A Pathogenic

single nucleotide variant

Genomic context: intron

Splice-donor allele reported in trans to a two-nucleotide deletion. The original report uses IVS3+1G>A nomenclature; this location is intron 3, not exon 5.

Show evidence (1 reference)

PMID:17331980 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"The first, IVS3 + 1G > A, altered the conserved splicing site of intron 3, and the second deleted two nucleotides (1687-1688 del TT) in exon 5, truncating the last 47 amino acids."

Direct counterexample to a universal exon 5 location claim.

c.171dupG and c.1656dupC compound-heterozygous genotype Pathogenic

The 2017 patient carried p.Leu58Alafs*29 and p.Ala553Argfs*15, inherited from the respective heterozygous parents. These predicted truncations do not prove complete absence of COG8 protein in this patient.

Show evidence (1 reference)

PMID:28619360 SUPPORT Human Clinical

"Targeted exome sequencing was performed to screen all CDG type II-related genes, and two novel frameshift mutations were found: c.171dupG (p.Leu58Alafs*29) and c.1656dupC (p.Ala553Argfs*15) in COG8."

Reports two further truncating COG8 alleles in a third patient.

💊

Medical Actions

5

Nutritional and developmental support

Category: Therapeutic Action: Nutritional and developmental support Ontology label: Supportive Care NCIT:C15747

The retired GeneReviews overview recommends nutritional support for failure to thrive and occupational, physical and speech therapy for developmental delay across N-linked and multiple-pathway CDGs. These are general supportive-care recommendations applicable to the corresponding COG8 manifestations, rather than COG8 intervention-trial results.

Target Phenotypes: Failure to thrive HP:0001508 Global developmental delay HP:0001263

Show evidence (2 references)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/ SUPPORT INDIRECT REVIEW SYNTHESIS Other

"Some children require placement of a nasogastric tube or gastrostomy tube for nutritional support until oral motor skills improve."

Historical group-level nutritional support; does not establish COG8-specific tube-feeding outcomes.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/ SUPPORT INDIRECT REVIEW SYNTHESIS Other

"Occupational therapy, physical therapy, and speech therapy should be instituted. As the developmental gap widens between children with CDG and their unaffected peers, parents, educators, and therapists need continued counseling and support."

General developmental-care recommendation in the retired overview, not a COG8-specific efficacy study.

Hepatic and coagulation surveillance

Category: Monitoring Action: Clinical Evaluation NCIT:C124351

The retired group-level overview includes liver-function and coagulation-factor surveillance, with hematology assessment before surgery. This is general CDG guidance for manifestations documented in COG8-CDG; the surveillance interval has not been validated specifically in COG8 patients.

Show evidence (2 references)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/ SUPPORT INDIRECT REVIEW SYNTHESIS Other

"Consultation with a hematologist is recommended to document the pro- and anti- clotting factor levels and coagulation status."

General coagulation assessment recommendation from the retired CDG overview.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/ SUPPORT INDIRECT REVIEW SYNTHESIS Other

"Liver function tests; thyroid panel; serum concentrations of the clotting factors protein C, protein S, factor IX, and antithrombin III"

The source lists these under annual surveillance for the broad CDG group; only hepatic/coagulation monitoring is modeled here.

Genetic counseling and reproductive planning

Category: Counseling / Informational Action: Genetic Counseling NCIT:C15240

Counseling includes segregation and carrier assessment, conditional recurrence risk and reproductive options. The historical overview states that prenatal and preimplantation testing become possible after identification of familial pathogenic variants. Parental carrier status and the familial variants should be established for recurrence-risk counseling.

Show evidence (1 reference)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/ SUPPORT INDIRECT REVIEW SYNTHESIS Other

"Once the ... pathogenic variant ... (s) have been identified in the family, ... prenatal testing ... for a pregnancy at increased risk and ... preimplantation genetic testing ... for a ... congenital ... disorder of N-linked glycosylation or multiple pathway are possible."

General molecularly defined CDG counseling, applicable once familial COG8 variants are established.

Medication precautions with hepatic involvement

Category: Counseling / Informational Action: Counseling NCIT:C61547

The retired overview advises caution with acetaminophen and other hepatically metabolized agents. This is historical general CDG guidance, not evidence that all such agents are contraindicated in COG8-CDG; medication decisions require individual hepatic assessment.

Show evidence (1 reference)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/ SUPPORT INDIRECT REVIEW SYNTHESIS Other

"Acetominophen and other agents metabolized by the liver should be used with caution."

Historical general medication precaution; the source spells acetaminophen as acetominophen. It does not report a COG8-specific adverse-drug study.

Ophthalmologic assessment and strabismus care

Category: Therapeutic Action: Strabismus supportive care Ontology label: Supportive Care NCIT:C15747

The retired general CDG GeneReviews chapter recommends early ophthalmologic assessment and individualized vision-preserving treatment for strabismus. This is historical group-level supportive guidance, not a COG8-specific treatment trial.

Target Phenotypes: Esotropia HP:0000565

Show evidence (1 reference)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/ SUPPORT INDIRECT REVIEW SYNTHESIS Other

"Consultation with a pediatric ophthalmologist early in life is important so that potential eye abnormalities can be diagnosed and therapies that preserve vision (glasses, patching, or surgery) can be instituted as needed."

Historical general CDG guidance relevant to the reported esotropia.

🔬

Diagnosis

3

Serum transferrin isoelectric focusing

Reported COG8-CDG cases show a type II transferrin profile. The pattern directs a broader CDG evaluation but is not specific to COG8, and diagnostic sensitivity cannot be estimated from these case reports.

Show evidence (1 reference)

PMID:28619360 SUPPORT Human Clinical

"The transferrin isoelectric focusing profiles in the patient showed a CDG type II pattern with increased disialo- and trisialo-transferrin."

Reports the diagnostic transferrin pattern.

Targeted or trio exome sequencing of CDG type II genes

Molecular identification of biallelic COG8 variants and segregation analysis establish the genetic diagnosis. The 2017 and 2019 reports used targeted and trio exome sequencing. The type II transferrin pattern alone does not identify the responsible gene.

Show evidence (3 references)

PMID:28619360 SUPPORT Human Clinical

"Targeted exome sequencing was performed to screen all CDG type II-related genes, and two novel frameshift mutations were found: c.171dupG (p.Leu58Alafs*29) and c.1656dupC (p.Ala553Argfs*15) in COG8."

Targeted exome sequencing established the diagnosis.

PMID:30690882 SUPPORT Human Clinical

"Trio whole exome sequencing revealed a novel homozygous variant in COG8, which creates a new splice site in exon 5 and protein truncation after 12 amino acids downstream to the newly generated splice site."

Trio exome sequencing established the antenatal diagnosis.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/ SUPPORT INDIRECT REVIEW SYNTHESIS Other

"If previous biochemical testing is not diagnostic for or suggestive of a particular CDG, molecular testing approaches most often involve use of a ... multigene panel ... or ... more ... comprehensive ... genomic ... testing"

Retired group-level diagnostic guidance; the COG8 case reports demonstrate exome-based diagnosis.

Apolipoprotein C-III and serum glycan analysis

In the p.Tyr537Ter patient, abnormal ApoC-III isoelectric focusing and serum O-glycan mass spectrometry demonstrated O-glycosylation involvement. Serum N-glycan changes were relatively subtle despite substantial neurological disease.

Show evidence (2 references)

url:https://oup.silverchair-cdn.com/article-minimal/654283 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"the abnormal IEF of ApoC-III (data not shown) indicates an O-glycosylation deficiency"

Additional biochemical characterization in a reported patient.

PMID:17220172 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Mass spectrometric analysis of the N- and O-glycan structures identified a mild sialylation deficiency."

Biochemical characterization does not define overall clinical severity.

📊

Prevalence

1

Worldwide

Cases In Literature Ultra Rare

The 2019 report described its patient as the fourth published case. This is a historical literature count, not a current global census or a measured population prevalence.

Show evidence (1 reference)

PMID:30690882 SUPPORT Other

"To date, only three cases of COG8-CDG have been published but none in the antenatal period."

Historical case count reported in 2019.

🧫

Experimental Models

4

COG8-deficient CDG patient fibroblasts with lentiviral complementation PRIMARY_CELL_CULTURE

Patient fibroblasts from the Kranz et al. case had undetectable COG8, abnormal subunit localization, hyposialylation and delayed BFA response. Lentiviral wild-type COG8 corrected these cellular readouts. Complementation supports a causal contribution of COG8 dysfunction but does not establish clinical treatment efficacy.

Organism

human NCBITaxon:9606

Pathograph links

Reduced COG8 protein abundance recapitulates fidelity: high observes: cellular The patient-derived line directly models the undetectable COG8 protein reported for this genotype.

Limitations: Fibroblasts are not an affected tissue in the neurological phenotype, and a single patient's cells cannot represent the allelic spectrum.

Divergences from the human mechanism

boundary omission qualifying

Cultured cells do not include the neural, hepatic and systemic interactions needed to explain the clinical phenotype.

Show evidence (1 reference)

PMID:17331980 SUPPORT In Vitro

"Patient fibroblasts completely lacked COG8 protein and had reduced levels and/or mislocalization of several other COG proteins."

Undetectable COG8 protein in this patient fibroblast line.

Abnormal N-glycan sialylation rescues observes: cellular

Limitations: Correction in cultured fibroblasts does not establish rescue of neurological or other clinical outcomes.

Divergences from the human mechanism

boundary omission qualifying

Cultured cells do not include the neural, hepatic and systemic interactions needed to explain the clinical phenotype.

Readouts

Restored N-glycan sialylation

Direction: RESTORED

Interpretation: Wild-type COG8 complementation restores this cellular readout, supporting COG8 dependence without establishing clinical treatment benefit.

Show evidence (1 reference)

PMID:17331980 SUPPORT In Vitro

"Lentiviral-mediated complementation with normal COG8 corrected mislocalization of other COG proteins, normalized sialylation and restored normal BFA-induced Golgi disruption."

Reports the rescue of all three cellular readouts.

Show evidence (1 reference)

PMID:17331980 SUPPORT In Vitro

"Lentiviral-mediated complementation with normal COG8 corrected mislocalization of other COG proteins, normalized sialylation and restored normal BFA-induced Golgi disruption."

Reports the rescue of all three cellular readouts.

Abnormal O-glycan sialylation rescues observes: cellular

Limitations: Correction in cultured fibroblasts does not establish rescue of neurological or other clinical outcomes.

Divergences from the human mechanism

boundary omission qualifying

Cultured cells do not include the neural, hepatic and systemic interactions needed to explain the clinical phenotype.

Readouts

Restored O-glycan sialylation

Direction: RESTORED

Interpretation: Wild-type COG8 complementation restores this cellular readout, supporting COG8 dependence without establishing clinical treatment benefit.

Show evidence (1 reference)

PMID:17331980 SUPPORT In Vitro

"Lentiviral-mediated complementation with normal COG8 corrected mislocalization of other COG proteins, normalized sialylation and restored normal BFA-induced Golgi disruption."

Reports the rescue of all three cellular readouts.

Show evidence (1 reference)

PMID:17331980 SUPPORT In Vitro

"Lentiviral-mediated complementation with normal COG8 corrected mislocalization of other COG proteins, normalized sialylation and restored normal BFA-induced Golgi disruption."

Reports the rescue of all three cellular readouts.

Delayed Golgi-to-ER retrograde transport rescues observes: cellular

Limitations: Correction in cultured fibroblasts does not establish rescue of neurological or other clinical outcomes.

Divergences from the human mechanism

boundary omission qualifying

Cultured cells do not include the neural, hepatic and systemic interactions needed to explain the clinical phenotype.

Readouts

Restored brefeldin A-induced Golgi redistribution

Direction: RESTORED

Interpretation: Wild-type COG8 complementation restores this cellular readout, supporting COG8 dependence without establishing clinical treatment benefit.

Show evidence (1 reference)

PMID:17331980 SUPPORT In Vitro

"Lentiviral-mediated complementation with normal COG8 corrected mislocalization of other COG proteins, normalized sialylation and restored normal BFA-induced Golgi disruption."

Reports the rescue of all three cellular readouts.

Show evidence (1 reference)

PMID:17331980 SUPPORT In Vitro

"Lentiviral-mediated complementation with normal COG8 corrected mislocalization of other COG proteins, normalized sialylation and restored normal BFA-induced Golgi disruption."

Reports the rescue of all three cellular readouts.

COG8 shRNA knockdown HeLa cells CELL_LINE

COG8 shRNA depletion in HeLa cells was studied using both transient and stable lines. The cells showed altered Golgi organization, impaired SNARE assembly and endosome-to-TGN transport; the system differs from the patient genotypes and cellular context.

Organism

human NCBITaxon:9606

Pathograph links

Impaired Golgi SNARE complex assembly recapitulates fidelity: moderate observes: cellular Reduced SNARE complex assembly is also observed in the tested patient fibroblasts.

Limitations: HeLa depletion does not reproduce all patient-cell effects: GS15 abundance increased in depleted HeLa cells but decreased in patient fibroblasts; VAMP4 abundance was unchanged in HeLa cells but reduced in patient cells.

Divergences from the human mechanism

boundary omission qualifying

Cultured cells do not include the neural, hepatic and systemic interactions needed to explain the clinical phenotype.

Show evidence (1 reference)

PMID:23865579 SUPPORT In Vitro

"By detailed analysis of Cog8 deficiency in either HeLa cells or CDG-derived fibroblasts, we show that Cog8 is required for the assembly of both the COG complex and the Golgi Stx5-GS28-Ykt6-GS15 and Stx6-Stx16-Vti1a-VAMP4 SNARE complexes."

Establishes the knockdown line as informative for the tethering and SNARE-assembly node.

Findings

Dilated Golgi cisternae and accumulated perigolgi vesicles were observed by electron microscopy; failed tethering or fusion was an interpretation, not a directly measured event.

Show evidence (1 reference)

PMID:23865579 SUPPORT DIRECT PRIMARY RESULT In Vitro

"Electron microscopy analysis further exposed a dilation of Golgi cisternae and accumulation of vesicles in the vicinity of the Golgi (Figure 1B), which possibly represent vesicles that failed to fuse with the Golgi membranes."

Morphology supports a trafficking defect without identifying the precise failed step.

COG8 siRNA-depleted HeLa cells CELL_LINE

HeLa COG8 knockdown models showed altered Golgi enzyme localization and lectin readouts, but total cellular N-glycan mass spectrometry did not reproduce patient serum hyposialylation.

Organism

human NCBITaxon:9606

Pathograph links

Abnormal N-glycan sialylation fails to recapitulate observes: cellular

Limitations: Acute knockdown in transformed cells and total-cell glycans differ from patient genotypes and serum proteins.

Divergences from the human mechanism

boundary omission qualifying

Cultured cells do not include the neural, hepatic and systemic interactions needed to explain the clinical phenotype.

proxy quantity qualifying

The mass-spectrometry measurement is total cellular N-glycans, whereas the clinical comparison is serum glycoprotein N-glycans. Their measured sialylation changes have opposite directions.

Show evidence (1 reference)

PMID:21421995 REFUTE DIRECT PRIMARY RESULT In Vitro

"Surprisingly, the data also show a minor increase in sialylation in the N-glycans of COG6- and COG8-deficient cells."

Total-cell HeLa N-glycans differ from patient serum findings; the model does not reproduce this readout.

Show evidence (1 reference)

PMID:21421995 SUPPORT DIRECT PRIMARY RESULT In Vitro

"In all analyzed COG KD cells, MGAT1, MAN2A1 and ST6GAL1 proteins were found in multiple vesicle-like structures, as well as in large fragmented Golgi mini-stacks that were positive for the Golgi matrix protein GM130."

The tested panel included COG8-depleted HeLa cells.

COG8-knockout HEK293T proteoglycan model CELL_LINE

CRISPR/Cas9 COG8-knockout HEK293T cells have reduced sulfate incorporation into proteoglycans, preserved chain lengths on secreted proteoglycans, longer cell-associated GAG chains and preserved surface 10E4 antibody recognition. These findings do not establish a patient-tissue proteoglycan defect or clinical severity mechanism.

Organism

human NCBITaxon:9606

Pathograph links

Biallelic COG8 dysfunction perturbs observes: cellular

Limitations: Complete engineered knockout differs from individual patient alleles; no clinical skeletal phenotype is reproduced.

Divergences from the human mechanism

boundary omission qualifying

Cultured cells do not include the neural, hepatic and systemic interactions needed to explain the clinical phenotype.

Show evidence (1 reference)

PMID:34053170 SUPPORT DIRECT PRIMARY RESULT In Vitro

"We here show that glycosaminoglycan (GAG) modification of PGs is significantly reduced, regardless which COG subunit that is missing in HEK293T cells."

KO model readout, not a measured patient phenotype.

Findings

Secreted proteoglycan GAG chain lengths were preserved in COG8-knockout cells.

Show evidence (1 reference)

PMID:34053170 SUPPORT DIRECT PRIMARY RESULT In Vitro

"COG1 and COG8 (figure 4, panels C and J) deficient cells displayed GAG chains of similar length to the wild type cells"

Secreted-chain finding distinguishes COG8 from several other COG subunit knockouts.

Surface heparan sulfate 10E4 recognition was preserved despite reduced overall proteoglycan synthesis.

Show evidence (1 reference)

PMID:34053170 SUPPORT DIRECT PRIMARY RESULT In Vitro

"A surprising finding was that, both COG1 and COG8 deficient cells were recognized to the same extent as wild type cells"

The 10E4 flow-cytometry result does not measure all heparan sulfate functions.

{ }

Source YAML

click to show

name: COG8-congenital disorder of glycosylation
creation_date: '2026-09-03T00:00:00Z'
category: Mendelian
description: COG8-CDG (CDG-IIh) is an autosomal recessive congenital disorder of glycosylation caused by biallelic COG8 variants. COG8 contributes to the conserved oligomeric Golgi complex. Patient-cell studies show altered complex assembly, SNARE assembly and retrograde trafficking, with genotype-dependent residual protein and effects on Golgi enzymes. Serum and cellular N- and O-glycosylation abnormalities vary in magnitude. The clinical spectrum includes developmental impairment or regression, hypotonia, ataxia, seizures, microcephaly, cerebellar atrophy, growth impairment and variable hepatic or coagulation abnormalities. Prenatal findings include increased nuchal translucency, Dandy-Walker malformation and arthrogryposis in a reported case. The small number of published patients does not establish phenotype frequencies or a reliable genotype-severity rule.
disease_term:
  preferred_term: COG8-congenital disorder of glycosylation
  term:
    id: MONDO:0012635
    label: COG8-congenital disorder of glycosylation
parents:
- congenital disorder of glycosylation type II
- defect in conserved oligomeric Golgi complex
- inborn error of metabolism
synonyms:
- COG8-CDG
- CDG-IIh
- CDG-II/COG8
- congenital disorder of glycosylation type IIh
- COG8 deficiency
references:
- reference: PMID:17220172
  title: A new inborn error of glycosylation due to a Cog8 deficiency reveals a critical role for the Cog1-Cog8 interaction in COG complex formation.
- reference: PMID:17331980
  title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
- reference: PMID:17904886
  title: Deficiencies in subunits of the Conserved Oligomeric Golgi (COG) complex define a novel group of Congenital Disorders of Glycosylation.
- reference: PMID:21421995
  title: Conserved oligomeric Golgi complex specifically regulates the maintenance of Golgi glycosylation machinery.
- reference: PMID:23865579
  title: Deficiency of the Cog8 subunit in normal and CDG-derived cells impairs the assembly of the COG and Golgi SNARE complexes.
- reference: PMID:28619360
  title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
- reference: PMID:30690882
  title: The first case of antenatal presentation in COG8-congenital disorder of glycosylation with a novel splice site mutation and an extended phenotype.
- reference: PMID:34053170
  title: Proteoglycan synthesis in conserved oligomeric Golgi subunit deficient HEK293T cells is affected differently, depending on the lacking subunit.
- reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
  title: https://oup.silverchair-cdn.com/article-minimal/654283
  findings:
  - statement: Publisher-hosted full text of Foulquier et al., A new inborn error of glycosylation due to a Cog8 deficiency reveals a critical role for the Cog1-Cog8 interaction in COG complex formation (Human Molecular Genetics 16:717-730, 2007; PMID:17220172; DOI:10.1093/hmg/ddl476).
- reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/
  title: Congenital Disorders of N-Linked Glycosylation and Multiple Pathway Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY - GeneReviews® - NCBI Bookshelf
- reference: PMID:20301507
  title: Congenital Disorders of N-Linked Glycosylation and Multiple Pathway Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY.
  tags:
  - GeneReviews
inheritance:
- name: Autosomal recessive
  description: Biallelic COG8 variants underlie the disorder. Homozygous and compound-heterozygous genotypes are reported; the parents in the 2017 compound-heterozygous family carried the respective variants. When both parents are carriers, each pregnancy has a 25% affected, 50% carrier and 25% noncarrier probability.
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  evidence:
  - reference: PMID:28619360
    reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The parents were heterozygous carriers of each variant.
    explanation: Segregation of the two truncating COG8 variants to unaffected heterozygous parents establishes autosomal recessive inheritance.
  - reference: PMID:17220172
    reference_title: A new inborn error of glycosylation due to a Cog8 deficiency reveals a critical role for the Cog1-Cog8 interaction in COG complex formation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Here, we describe a patient with a mild form of a congenital disorder of glycosylation type II (CDG-II), which is caused by a homozygous nonsense mutation in the hCOG8 gene.
    explanation: A homozygous nonsense COG8 variant in an affected patient supports a biallelic, recessive disease mechanism.
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/
    reference_title: Congenital Disorders of N-Linked Glycosylation and Multiple Pathway Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: INDIRECT
    snippet: At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic ... carrier ... and a 25% chance of being unaffected and not a carrier.
    explanation: Historical group-level autosomal-recessive counseling applies when both parents carry a disease-causing COG8 allele.
pathophysiology:
- name: Biallelic COG8 dysfunction
  biological_scale: MOLECULAR
  description: 'Biallelic COG8 variants impair function of a lobe B component of the conserved oligomeric Golgi complex. Published genotypes include nonsense, frameshift and splice-altering alleles. Their cellular effects vary: absence of detectable COG8 and residual truncated protein have both been reported.'
  evidence:
  - reference: PMID:17331980
    reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We describe a new Type II congenital disorder of glycosylation (CDG-II) caused by mutations in the conserved oligomeric Golgi (COG) complex gene, COG8.
    explanation: Establishes COG8 as the causal gene.
  genes:
  - preferred_term: COG8
    term:
      id: hgnc:18623
      label: COG8
  downstream:
  - target: Reduced COG8 protein abundance
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:17331980
      reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: Patient fibroblasts completely lacked COG8 protein and had reduced levels and/or mislocalization of several other COG proteins.
      explanation: Undetectable protein in this particular patient line.
  - target: Disrupted COG complex assembly
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:17220172
      reference_title: A new inborn error of glycosylation due to a Cog8 deficiency reveals a critical role for the Cog1-Cog8 interaction in COG complex formation.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: We showed that the molecular basis of this defect in N- and O-glycosylation is caused by the disruption of the Cog1-Cog8 interaction due to truncation.
      explanation: Supported for the tested truncation, not a universal residue-level account of all alleles.
  - target: Global Developmental Delay
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:17331980
      reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: The patient has severe psychomotor retardation, seizures, failure to thrive and intolerance to wheat and dairy products.
      explanation: Severe psychomotor retardation in the index COG8-CDG patient.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Hypotonia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:28619360
      reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Here, we describe an 8-year-old Korean boy with psychomotor retardation, hypotonia, failure to thrive, elevated serum liver enzymes, microcephaly, and talipes equinovarus.
      explanation: Reports hypotonia among the presenting features.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Failure to Thrive
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:17331980
      reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: The patient has severe psychomotor retardation, seizures, failure to thrive and intolerance to wheat and dairy products.
      explanation: Failure to thrive in the index patient.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Seizures
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:17331980
      reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: The patient has severe psychomotor retardation, seizures, failure to thrive and intolerance to wheat and dairy products.
      explanation: Seizures in the index patient.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Microcephaly
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:28619360
      reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Here, we describe an 8-year-old Korean boy with psychomotor retardation, hypotonia, failure to thrive, elevated serum liver enzymes, microcephaly, and talipes equinovarus.
      explanation: Reports microcephaly.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Cerebellar Atrophy
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:28619360
      reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: A liver biopsy of the patient showed only interface hepatitis with mild lobular activity, and brain magnetic resonance imaging revealed cerebellar atrophy.
      explanation: MRI-documented cerebellar atrophy.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Elevated Serum Transaminases
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:28619360
      reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Here, we describe an 8-year-old Korean boy with psychomotor retardation, hypotonia, failure to thrive, elevated serum liver enzymes, microcephaly, and talipes equinovarus.
      explanation: Reports elevated serum liver enzymes.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Talipes Equinovarus
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:28619360
      reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Here, we describe an 8-year-old Korean boy with psychomotor retardation, hypotonia, failure to thrive, elevated serum liver enzymes, microcephaly, and talipes equinovarus.
      explanation: Reports talipes equinovarus.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Dandy-Walker Malformation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30690882
      reference_title: The first case of antenatal presentation in COG8-congenital disorder of glycosylation with a novel splice site mutation and an extended phenotype.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: We present the first case of antenatally diagnosed COG8-CDG with facial dysmorphism and additional features such as Dandy-Walker malformation and arthrogryposis multiplex congenita, thus expanding the phenotype of this rare disorder.
      explanation: Reports Dandy-Walker malformation.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Arthrogryposis Multiplex Congenita
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30690882
      reference_title: The first case of antenatal presentation in COG8-congenital disorder of glycosylation with a novel splice site mutation and an extended phenotype.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: We present the first case of antenatally diagnosed COG8-CDG with facial dysmorphism and additional features such as Dandy-Walker malformation and arthrogryposis multiplex congenita, thus expanding the phenotype of this rare disorder.
      explanation: Reports arthrogryposis multiplex congenita.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Facial Dysmorphism
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30690882
      reference_title: The first case of antenatal presentation in COG8-congenital disorder of glycosylation with a novel splice site mutation and an extended phenotype.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: We present the first case of antenatally diagnosed COG8-CDG with facial dysmorphism and additional features such as Dandy-Walker malformation and arthrogryposis multiplex congenita, thus expanding the phenotype of this rare disorder.
      explanation: Reports facial dysmorphism.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Increased Nuchal Translucency
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:30690882
      reference_title: The first case of antenatal presentation in COG8-congenital disorder of glycosylation with a novel splice site mutation and an extended phenotype.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: An association between antenatally increased nuchal translucency and COG8-CDG is also established, which would alert clinicians to its diagnosis early in gestation.
      explanation: Reports the antenatal nuchal translucency finding.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Developmental regression
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
      reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: Although the neonatal period and early infancy were normal, at the age of 6 months, she presented with an acute encephalopathy and loss of psychomotor abilities, hypotonia, alternating esotropia, pseudo-ptosis and mental retardation.
      explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Encephalopathy
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
      reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: Although the neonatal period and early infancy were normal, at the age of 6 months, she presented with an acute encephalopathy and loss of psychomotor abilities, hypotonia, alternating esotropia, pseudo-ptosis and mental retardation.
      explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Esotropia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
      reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: Although the neonatal period and early infancy were normal, at the age of 6 months, she presented with an acute encephalopathy and loss of psychomotor abilities, hypotonia, alternating esotropia, pseudo-ptosis and mental retardation.
      explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Ataxia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
      reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: From the age of 7, her cerebellar ataxia has worsened.
      explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Action myoclonus
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
      reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: She later developed a cerebellar syndrome with prominent ataxia and action myoclonus.
      explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Oculomotor apraxia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
      reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: A detailed clinical evaluation now revealed an oculomotor apraxia with dysinergia oculocephalica, in addition to the pseudo-ptosis and alternating esotropia; fundoscopy was normal.
      explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Absent Achilles reflex
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
      reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: She has symptoms of neuropathy in the lower limbs because she walks with ataxia and foot drop; she has abolished achilles tendon reflexes.
      explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Foot dorsiflexor weakness
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
      reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: She has symptoms of neuropathy in the lower limbs because she walks with ataxia and foot drop; she has abolished achilles tendon reflexes.
      explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Brainstem atrophy
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
      reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: At the age of 6 years, brain magnetic resonance imaging (MRI) showed cerebellar atrophy and slight brainstem atrophy
      explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Short stature
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
      reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: The Cog8-defective patient suffers from cerebellar atrophy, mental and motor retardation, hypotonia, growth delay and short stature.
      explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Abnormality of coagulation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
      reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: During some other episodes, she presented spontaneous hematomas, coincident with alteration of the coagulation factors and a decrease in the prothrombin time, together with increased levels of transaminases and of creatine kinase.
      explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Bruising susceptibility
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
      reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: During some other episodes, she presented spontaneous hematomas, coincident with alteration of the coagulation factors and a decrease in the prothrombin time, together with increased levels of transaminases and of creatine kinase.
      explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Elevated creatine kinase
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
      reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: During some other episodes, she presented spontaneous hematomas, coincident with alteration of the coagulation factors and a decrease in the prothrombin time, together with increased levels of transaminases and of creatine kinase.
      explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Recurrent fever
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
      reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: During infancy, she exhibited PFAPA syndrome (periodic fever, aphthous stomatitis, pharyngitis and adenitis)
      explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
    description: Clinical association with the causal COG8 disorder; the intervening tissue mechanism is unresolved.
  - target: Reduced protein C activity
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Clinical association in the reported COG8-CDG patient; tissue intermediates remain unresolved.
    evidence:
    - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
      reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: Because of her occasional coagulation problems, bleeding or thrombosis, and the fluctuation of the coagulation parameters throughout development (protein C and protein S deficiency, decreased prothrombin time and coagulation factors), a wide study for
      explanation: Direct clinical observation in one patient; no population frequency or independent causal mechanism is established.
  - target: Reduced protein S activity
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Clinical association in the reported COG8-CDG patient; tissue intermediates remain unresolved.
    evidence:
    - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
      reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: Because of her occasional coagulation problems, bleeding or thrombosis, and the fluctuation of the coagulation parameters throughout development (protein C and protein S deficiency, decreased prothrombin time and coagulation factors), a wide study for
      explanation: Direct clinical observation in one patient; no population frequency or independent causal mechanism is established.
  - target: Sandal gap
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Clinical association in the reported COG8-CDG patient; tissue intermediates remain unresolved.
    evidence:
    - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
      reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: 'Minor dysmorphic features: small feet, wide space between the first and second toes and clinodactyly of the third and fourth toes can be observed.'
      explanation: Direct clinical observation in one patient; no population frequency or independent causal mechanism is established.
  - target: Clinodactyly of the 3rd toe
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Clinical association in the reported COG8-CDG patient; tissue intermediates remain unresolved.
    evidence:
    - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
      reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: 'Minor dysmorphic features: small feet, wide space between the first and second toes and clinodactyly of the third and fourth toes can be observed.'
      explanation: Direct clinical observation in one patient; no population frequency or independent causal mechanism is established.
  - target: Clinodactyly of the 4th toe
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: Clinical association in the reported COG8-CDG patient; tissue intermediates remain unresolved.
    evidence:
    - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
      reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: 'Minor dysmorphic features: small feet, wide space between the first and second toes and clinodactyly of the third and fourth toes can be observed.'
      explanation: Direct clinical observation in one patient; no population frequency or independent causal mechanism is established.
- name: Reduced COG8 protein abundance
  biological_scale: MOLECULAR
  description: COG8 was undetectable in the compound-heterozygous patient fibroblasts reported by Kranz et al. In the p.Tyr537Ter patient, a truncated protein remained detectable at about one quarter of control immunoreactivity. These are genotype-specific fibroblast measurements, not proof of complete absence in all tissues.
  evidence:
  - reference: PMID:17331980
    reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Patient fibroblasts completely lacked COG8 protein and had reduced levels and/or mislocalization of several other COG proteins.
    explanation: Undetectable protein in this particular patient line.
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Moreover, compared with control, only 25% of the immunoreactivity was recovered, suggesting that the transcript or the truncated Cog8 protein is unstable
    explanation: Residual truncated protein in the p.Tyr537Ter line limits a universal null-protein claim.
- name: Disrupted COG complex assembly
  biological_scale: MOLECULAR
  description: 'The p.Tyr537Ter truncation disrupts the COG1-COG8 interaction and intact complex assembly. Smaller subcomplexes remain. Secondary COG1 reduction is not uniform absence: COG1 remained weakly Golgi-localized in the p.Tyr537Ter patient, whereas it was not detected at the Golgi in the other patient line used in the 2013 study.'
  evidence:
  - reference: PMID:17220172
    reference_title: A new inborn error of glycosylation due to a Cog8 deficiency reveals a critical role for the Cog1-Cog8 interaction in COG complex formation.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: As a result, Cog1 deficiency accompanies the Cog8 deficiency, preventing assembly of the intact, stable complex and resulting in the appearance of smaller subcomplexes.
    explanation: The interaction and fractionation studies identify a defect in complex integrity.
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Although weaker in immunofluorescence signal, as expected from the western blot analysis, the Cog1 subunit was associated with the Golgi in both the patient and control fibroblasts
    explanation: Retained localization in the p.Tyr537Ter patient prevents equating reduced COG1 abundance with loss from the Golgi in every genotype.
  - reference: PMID:23865579
    reference_title: Deficiency of the Cog8 subunit in normal and CDG-derived cells impairs the assembly of the COG and Golgi SNARE complexes.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: In CDG-derived Cog8-deficient fibroblasts, Cog1 was not detected in the Golgi
    explanation: Contrasting result in the patient line studied by Laufman et al.
  downstream:
  - target: Impaired Golgi SNARE complex assembly
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:23865579
      reference_title: Deficiency of the Cog8 subunit in normal and CDG-derived cells impairs the assembly of the COG and Golgi SNARE complexes.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: the interactions of Stx5 with either the v-SNARE GS15 or the t-SNAREs Ykt6 and GS28 were significantly reduced in both Cog8-deficient cell types.
      explanation: NEM-stabilized immunoprecipitation detects reduced Stx5 complex assembly.
    - reference: PMID:23865579
      reference_title: Deficiency of the Cog8 subunit in normal and CDG-derived cells impairs the assembly of the COG and Golgi SNARE complexes.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: Despite the differences in the steady-state distributions of the SNARE proteins, the assembly of the Stx6 SNARE complex was impaired in both Cog8-deficient cell types.
      explanation: Independent Stx6 complex assembly readout in both systems.
    description: COG8 deficiency disrupts complex integrity and SNARE assembly; the precise intermediate interactions are incompletely resolved.
  - target: Delayed Golgi-to-ER retrograde transport
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:17331980
      reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: Patient fibroblasts were deficient in sialylation of both N- and O-glycans, and also showed slower brefeldin A (BFA)-induced disruption of the Golgi matrix, reminiscent of COG7-deficient cells.
      explanation: Patient-cell BFA redistribution result.
  - target: Impaired endosome-to-Golgi transport
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:23865579
      reference_title: Deficiency of the Cog8 subunit in normal and CDG-derived cells impairs the assembly of the COG and Golgi SNARE complexes.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: depletion of the Cog8 subunit substantially inhibited the transport of TGN38-HA to the TGN in HeLa cells.
      explanation: Dynamic transport measurement is specific to the HeLa model.
  - target: Altered Golgi glycosylation enzyme localization
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:21421995
      reference_title: Conserved oligomeric Golgi complex specifically regulates the maintenance of Golgi glycosylation machinery.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: In all analyzed COG KD cells, MGAT1, MAN2A1 and ST6GAL1 proteins were found in multiple vesicle-like structures, as well as in large fragmented Golgi mini-stacks that were positive for the Golgi matrix protein GM130.
      explanation: The tested panel included COG8-depleted HeLa cells.
  - target: Reduced beta1,4-galactosyltransferase abundance
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:17220172
      reference_title: A new inborn error of glycosylation due to a Cog8 deficiency reveals a critical role for the Cog1-Cog8 interaction in COG complex formation.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: Moreover, levels of beta1,4-galactosytransferase were significantly reduced.
      explanation: Reduced enzyme abundance in the patient-cell study.
  - target: Abnormal N-glycan sialylation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:17331980
      reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: Analysis of serum transferrin and total serum N-glycans showed normal addition of one sialic acid, but severe deficiency in subsequent sialylation of mostly normal N-glycans.
      explanation: Serum finding in one patient.
    - reference: PMID:17220172
      reference_title: A new inborn error of glycosylation due to a Cog8 deficiency reveals a critical role for the Cog1-Cog8 interaction in COG complex formation.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: Mass spectrometric analysis of the N- and O-glycan structures identified a mild sialylation deficiency.
      explanation: Biochemically mild result does not imply absence of major neurological disability.
    description: The biochemical link to COG8 dysfunction is established; the enzyme-specific contributions remain unresolved.
  - target: Abnormal O-glycan sialylation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:17220172
      reference_title: A new inborn error of glycosylation due to a Cog8 deficiency reveals a critical role for the Cog1-Cog8 interaction in COG complex formation.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: Mass spectrometric analysis of the N- and O-glycan structures identified a mild sialylation deficiency.
      explanation: Serum glycan analysis confirms the O-glycan component.
    - reference: PMID:17220172
      reference_title: A new inborn error of glycosylation due to a Cog8 deficiency reveals a critical role for the Cog1-Cog8 interaction in COG complex formation.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: The defects in O-glycosylation could be fully restored by transfecting the patient's fibroblasts with full-length Cog8.
      explanation: Complementation supports a COG8-dependent cellular phenotype.
- name: Impaired Golgi SNARE complex assembly
  biological_scale: CELLULAR
  description: Assembly of the Stx5-GS28-Ykt6-GS15 and Stx6-Stx16-Vti1a-VAMP4 complexes is reduced in COG8-depleted HeLa cells and the tested COG8-CDG fibroblasts. Protein abundance and localization differ between the systems; loss of complex assembly is not identical to loss of every SNARE protein.
  evidence:
  - reference: PMID:23865579
    reference_title: Deficiency of the Cog8 subunit in normal and CDG-derived cells impairs the assembly of the COG and Golgi SNARE complexes.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: the interactions of Stx5 with either the v-SNARE GS15 or the t-SNAREs Ykt6 and GS28 were significantly reduced in both Cog8-deficient cell types.
    explanation: NEM-stabilized immunoprecipitation detects reduced Stx5 complex assembly.
  - reference: PMID:23865579
    reference_title: Deficiency of the Cog8 subunit in normal and CDG-derived cells impairs the assembly of the COG and Golgi SNARE complexes.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Despite the differences in the steady-state distributions of the SNARE proteins, the assembly of the Stx6 SNARE complex was impaired in both Cog8-deficient cell types.
    explanation: Independent Stx6 complex assembly readout in both systems.
  biological_processes:
  - preferred_term: SNARE complex assembly
    term:
      id: GO:0035493
      label: SNARE complex assembly
    modifier: ABNORMAL
- name: Delayed Golgi-to-ER retrograde transport
  biological_scale: CELLULAR
  description: Patient fibroblasts exhibit delayed brefeldin A-induced redistribution of Golgi proteins. This pharmacological assay supports abnormal retrograde trafficking; it does not directly measure every physiological intra-Golgi transport step.
  evidence:
  - reference: PMID:17331980
    reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Patient fibroblasts were deficient in sialylation of both N- and O-glycans, and also showed slower brefeldin A (BFA)-induced disruption of the Golgi matrix, reminiscent of COG7-deficient cells.
    explanation: Patient-cell BFA redistribution result.
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: In the patient's cells, however, the BFA-induced redistribution of Golgi mannosidase II was significantly delayed at all times investigated
    explanation: The p.Tyr537Ter line also has a delayed BFA response.
  biological_processes:
  - preferred_term: retrograde vesicle-mediated transport, Golgi to endoplasmic reticulum
    term:
      id: GO:0006890
      label: retrograde vesicle-mediated transport, Golgi to endoplasmic reticulum
    modifier: ABNORMAL
- name: Impaired endosome-to-Golgi transport
  biological_scale: CELLULAR
  description: COG8-depleted HeLa cells show delayed TGN38 antibody-uptake trafficking to the trans-Golgi network. Patient fibroblasts show altered endogenous TGN38/46 and CI-MPR distribution, supporting disturbed recycling but without the same kinetic assay in patient cells.
  evidence:
  - reference: PMID:23865579
    reference_title: Deficiency of the Cog8 subunit in normal and CDG-derived cells impairs the assembly of the COG and Golgi SNARE complexes.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: depletion of the Cog8 subunit substantially inhibited the transport of TGN38-HA to the TGN in HeLa cells.
    explanation: Dynamic transport measurement is specific to the HeLa model.
  - reference: PMID:23865579
    reference_title: Deficiency of the Cog8 subunit in normal and CDG-derived cells impairs the assembly of the COG and Golgi SNARE complexes.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Collectively, these results suggest that Cog8 deficiency in either HeLa cells or CDG-derived fibroblasts influences endosome-to-TGN retrograde transport.
    explanation: Patient localization data support, but do not duplicate, the HeLa kinetic evidence.
  biological_processes:
  - preferred_term: retrograde transport, endosome to Golgi
    term:
      id: GO:0042147
      label: retrograde transport, endosome to Golgi
    modifier: ABNORMAL
- name: Altered Golgi glycosylation enzyme localization
  biological_scale: CELLULAR
  description: 'In COG8 siRNA-depleted HeLa cells, tested Golgi enzymes redistribute to vesicle-like structures and fragmented Golgi. This is not universal in patient fibroblasts: mannosidase II and beta1,4-galactosyltransferase retained perinuclear Golgi distribution in the p.Tyr537Ter patient. Effects depend on the protein, genotype and cell system.'
  evidence:
  - reference: PMID:21421995
    reference_title: Conserved oligomeric Golgi complex specifically regulates the maintenance of Golgi glycosylation machinery.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: In all analyzed COG KD cells, MGAT1, MAN2A1 and ST6GAL1 proteins were found in multiple vesicle-like structures, as well as in large fragmented Golgi mini-stacks that were positive for the Golgi matrix protein GM130.
    explanation: The tested panel included COG8-depleted HeLa cells.
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: REFUTE
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Both enzymes appeared to exhibit a normal perinuclear Golgi distribution in the patient's cells
    explanation: Mannosidase II and beta1,4-galactosyltransferase localization counterexample in p.Tyr537Ter fibroblasts.
- name: Reduced beta1,4-galactosyltransferase abundance
  biological_scale: MOLECULAR
  description: Beta1,4-galactosyltransferase abundance was reduced in the p.Tyr537Ter patient fibroblasts despite retained perinuclear localization. Abundance, localization and catalytic activity are distinct readouts; this experiment does not quantify a disease-wide enzyme deficiency.
  evidence:
  - reference: PMID:17220172
    reference_title: A new inborn error of glycosylation due to a Cog8 deficiency reveals a critical role for the Cog1-Cog8 interaction in COG complex formation.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Moreover, levels of beta1,4-galactosytransferase were significantly reduced.
    explanation: Reduced enzyme abundance in the patient-cell study.
- name: Abnormal N-glycan sialylation
  biological_scale: MOLECULAR
  description: Serum N-glycans and transferrin show incomplete terminal sialylation, with biochemical severity varying between cases. The markedly impaired addition of subsequent sialic acids described by Kranz et al. is not an invariant pattern in all genotypes. Acute COG8 knockdown in HeLa cells instead produced a minor increase in total cellular N-glycan sialylation.
  evidence:
  - reference: PMID:17331980
    reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Analysis of serum transferrin and total serum N-glycans showed normal addition of one sialic acid, but severe deficiency in subsequent sialylation of mostly normal N-glycans.
    explanation: Serum finding in one patient.
  - reference: PMID:17220172
    reference_title: A new inborn error of glycosylation due to a Cog8 deficiency reveals a critical role for the Cog1-Cog8 interaction in COG complex formation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Mass spectrometric analysis of the N- and O-glycan structures identified a mild sialylation deficiency.
    explanation: Biochemically mild result does not imply absence of major neurological disability.
  - reference: PMID:21421995
    reference_title: Conserved oligomeric Golgi complex specifically regulates the maintenance of Golgi glycosylation machinery.
    supports: REFUTE
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Surprisingly, the data also show a minor increase in sialylation in the N-glycans of COG6- and COG8-deficient cells.
    explanation: Total-cell HeLa N-glycans differ from patient serum findings; the model does not reproduce this readout.
  biological_processes:
  - preferred_term: protein N-linked glycosylation
    term:
      id: GO:0006487
      label: protein N-linked glycosylation
    modifier: ABNORMAL
  downstream:
  - target: Type II Transferrin Isoelectric Focusing Pattern
    description: Incomplete sialylation of serum transferrin gives the CDG type II isoelectric focusing profile.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:28619360
      reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: The transferrin isoelectric focusing profiles in the patient showed a CDG type II pattern with increased disialo- and trisialo-transferrin.
      explanation: Directly reports the type II transferrin profile produced by the sialylation defect.
- name: Abnormal O-glycan sialylation
  biological_scale: MOLECULAR
  description: Patient serum O-glycan analysis, ApoC-III isoelectric focusing and fibroblast lectin assays identify an O-glycosylation defect. In the p.Tyr537Ter patient, wild-type COG8 complementation reduced abnormal PNA staining. This is cellular rescue, not a demonstrated clinical gene therapy.
  evidence:
  - reference: PMID:17220172
    reference_title: A new inborn error of glycosylation due to a Cog8 deficiency reveals a critical role for the Cog1-Cog8 interaction in COG complex formation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Mass spectrometric analysis of the N- and O-glycan structures identified a mild sialylation deficiency.
    explanation: Serum glycan analysis confirms the O-glycan component.
  - reference: PMID:17220172
    reference_title: A new inborn error of glycosylation due to a Cog8 deficiency reveals a critical role for the Cog1-Cog8 interaction in COG complex formation.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: The defects in O-glycosylation could be fully restored by transfecting the patient's fibroblasts with full-length Cog8.
    explanation: Complementation supports a COG8-dependent cellular phenotype.
  biological_processes:
  - preferred_term: protein O-linked glycosylation
    term:
      id: GO:0006493
      label: protein O-linked glycosylation
    modifier: ABNORMAL
phenotypes:
- name: Global Developmental Delay
  category: Neurological
  description: Developmental impairment varies between reported individuals. The Korean case was described as relatively milder than the two 2007 cases; biochemical sialylation severity alone does not define neurological severity.
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  notes: Reported in the index patient (PMID:17331980) and in the third published patient (PMID:28619360). The small case series does not establish a population frequency.
  evidence:
  - reference: PMID:17331980
    reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The patient has severe psychomotor retardation, seizures, failure to thrive and intolerance to wheat and dairy products.
    explanation: Severe psychomotor retardation in the index COG8-CDG patient.
  - reference: PMID:28619360
    reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Compared with the previous two reported cases, our patient showed relatively mild psychomotor retardation without a seizure history.
    explanation: A second patient with psychomotor retardation, explicitly milder than the earlier cases.
- name: Hypotonia
  category: Neurological
  phenotype_term:
    preferred_term: Hypotonia
    term:
      id: HP:0001252
      label: Hypotonia
  notes: Reported in a patient (PMID:28619360).
  evidence:
  - reference: PMID:28619360
    reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Here, we describe an 8-year-old Korean boy with psychomotor retardation, hypotonia, failure to thrive, elevated serum liver enzymes, microcephaly, and talipes equinovarus.
    explanation: Reports hypotonia among the presenting features.
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/
    reference_title: Congenital Disorders of N-Linked Glycosylation and Multiple Pathway Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Two affected infants with severe developmental delay, hypotonia, seizures, esotropia, failure to thrive, and progressive microcephaly were reported
    explanation: COG8-specific paragraph of the retired GeneReviews overview; supports association, not a frequency estimate.
- name: Failure to Thrive
  category: Growth
  phenotype_term:
    preferred_term: Failure to thrive
    term:
      id: HP:0001508
      label: Failure to thrive
  notes: Reported in the index patient (PMID:17331980) and in the third published patient (PMID:28619360).
  evidence:
  - reference: PMID:17331980
    reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The patient has severe psychomotor retardation, seizures, failure to thrive and intolerance to wheat and dairy products.
    explanation: Failure to thrive in the index patient.
  - reference: PMID:28619360
    reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Here, we describe an 8-year-old Korean boy with psychomotor retardation, hypotonia, failure to thrive, elevated serum liver enzymes, microcephaly, and talipes equinovarus.
    explanation: Failure to thrive in a second patient.
- name: Seizures
  category: Neurological
  description: Seizures are variably present. The p.Tyr537Ter patient had one episode of status epilepticus during gastroenteritis and no subsequent seizures by age eight; the Korean patient had no seizure history.
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  notes: Present in the index patient (PMID:17331980); explicitly absent in the patient of PMID:28619360. Not a constant feature.
  evidence:
  - reference: PMID:17331980
    reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The patient has severe psychomotor retardation, seizures, failure to thrive and intolerance to wheat and dairy products.
    explanation: Seizures in the index patient.
  - reference: PMID:28619360
    reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: Compared with the previous two reported cases, our patient showed relatively mild psychomotor retardation without a seizure history.
    explanation: 'Cited against seizures being a constant feature: this patient had no seizure history.'
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: She has not suffered further epileptic seizures other than the status convulsivus at 17 months and she does not need antiepileptic drugs.
    explanation: Single-patient longitudinal course; not a general recommendation to withhold seizure treatment.
- name: Microcephaly
  category: Neurological
  phenotype_term:
    preferred_term: Microcephaly
    term:
      id: HP:0000252
      label: Microcephaly
  notes: Reported in a patient (PMID:28619360).
  evidence:
  - reference: PMID:28619360
    reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Here, we describe an 8-year-old Korean boy with psychomotor retardation, hypotonia, failure to thrive, elevated serum liver enzymes, microcephaly, and talipes equinovarus.
    explanation: Reports microcephaly.
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/
    reference_title: Congenital Disorders of N-Linked Glycosylation and Multiple Pathway Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Two affected infants with severe developmental delay, hypotonia, seizures, esotropia, failure to thrive, and progressive microcephaly were reported
    explanation: COG8-specific paragraph of the retired GeneReviews overview; supports association, not a frequency estimate.
- name: Cerebellar Atrophy
  category: Neurological
  description: Cerebellar atrophy is documented in the p.Tyr537Ter patient and the Korean patient. In the former, ataxia worsened despite little interval MRI change between ages six and eight.
  phenotype_term:
    preferred_term: Cerebellar atrophy
    term:
      id: HP:0001272
      label: Cerebellar atrophy
  notes: Documented by MRI in PMID:17220172 and PMID:28619360.
  evidence:
  - reference: PMID:28619360
    reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: A liver biopsy of the patient showed only interface hepatitis with mild lobular activity, and brain magnetic resonance imaging revealed cerebellar atrophy.
    explanation: MRI-documented cerebellar atrophy.
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: At the age of 6 years, brain magnetic resonance imaging (MRI) showed cerebellar atrophy and slight brainstem atrophy
    explanation: Clinical MRI result in the p.Tyr537Ter patient.
- name: Elevated Serum Transaminases
  category: Hepatic
  description: Elevated liver enzymes can be transient. The Korean patient had interface hepatitis with mild lobular activity on biopsy; the p.Tyr537Ter patient had fluctuating enzyme elevations during episodes of illness.
  phenotype_term:
    preferred_term: Elevated circulating hepatic transaminase concentration
    term:
      id: HP:0002910
      label: Elevated circulating hepatic transaminase concentration
  notes: Reported in a patient (PMID:28619360).
  evidence:
  - reference: PMID:28619360
    reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Here, we describe an 8-year-old Korean boy with psychomotor retardation, hypotonia, failure to thrive, elevated serum liver enzymes, microcephaly, and talipes equinovarus.
    explanation: Reports elevated serum liver enzymes.
  - reference: PMID:28619360
    reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: A liver biopsy of the patient showed only interface hepatitis with mild lobular activity, and brain magnetic resonance imaging revealed cerebellar atrophy.
    explanation: Characterises the hepatic involvement histologically as mild interface hepatitis.
- name: Talipes Equinovarus
  category: Skeletal
  phenotype_term:
    preferred_term: Talipes equinovarus
    term:
      id: HP:0001762
      label: Talipes equinovarus
  notes: Reported in a patient (PMID:28619360).
  evidence:
  - reference: PMID:28619360
    reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Here, we describe an 8-year-old Korean boy with psychomotor retardation, hypotonia, failure to thrive, elevated serum liver enzymes, microcephaly, and talipes equinovarus.
    explanation: Reports talipes equinovarus.
- name: Dandy-Walker Malformation
  category: Neurological
  phenotype_term:
    preferred_term: Dandy-Walker malformation
    term:
      id: HP:0001305
      label: Dandy-Walker malformation
  notes: Reported only in the antenatally ascertained patient (PMID:30690882), whose authors present it as an expansion of the COG8-CDG phenotype.
  evidence:
  - reference: PMID:30690882
    reference_title: The first case of antenatal presentation in COG8-congenital disorder of glycosylation with a novel splice site mutation and an extended phenotype.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We present the first case of antenatally diagnosed COG8-CDG with facial dysmorphism and additional features such as Dandy-Walker malformation and arthrogryposis multiplex congenita, thus expanding the phenotype of this rare disorder.
    explanation: Reports Dandy-Walker malformation.
- name: Arthrogryposis Multiplex Congenita
  category: Skeletal
  phenotype_term:
    preferred_term: Arthrogryposis multiplex congenita
    term:
      id: HP:0002804
      label: Arthrogryposis multiplex congenita
  notes: Reported only in the antenatally ascertained patient (PMID:30690882).
  evidence:
  - reference: PMID:30690882
    reference_title: The first case of antenatal presentation in COG8-congenital disorder of glycosylation with a novel splice site mutation and an extended phenotype.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We present the first case of antenatally diagnosed COG8-CDG with facial dysmorphism and additional features such as Dandy-Walker malformation and arthrogryposis multiplex congenita, thus expanding the phenotype of this rare disorder.
    explanation: Reports arthrogryposis multiplex congenita.
- name: Facial Dysmorphism
  category: Craniofacial
  phenotype_term:
    preferred_term: Abnormal facial shape
    term:
      id: HP:0001999
      label: Abnormal facial shape
  notes: Facial dysmorphism was reported in the antenatal case; the retrieved abstract does not specify individual facial features.
  evidence:
  - reference: PMID:30690882
    reference_title: The first case of antenatal presentation in COG8-congenital disorder of glycosylation with a novel splice site mutation and an extended phenotype.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We present the first case of antenatally diagnosed COG8-CDG with facial dysmorphism and additional features such as Dandy-Walker malformation and arthrogryposis multiplex congenita, thus expanding the phenotype of this rare disorder.
    explanation: Reports facial dysmorphism.
- name: Increased Nuchal Translucency
  category: Prenatal
  description: Increased nuchal translucency on antenatal ultrasound was the finding that led to prenatal ascertainment in the fourth published patient, and the authors propose it as a prompt to consider COG8-CDG early in gestation.
  phenotype_term:
    preferred_term: Increased nuchal translucency
    term:
      id: HP:0010880
      label: Increased nuchal translucency
  notes: Reported in a patient (PMID:30690882).
  evidence:
  - reference: PMID:30690882
    reference_title: The first case of antenatal presentation in COG8-congenital disorder of glycosylation with a novel splice site mutation and an extended phenotype.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: An association between antenatally increased nuchal translucency and COG8-CDG is also established, which would alert clinicians to its diagnosis early in gestation.
    explanation: Reports the antenatal nuchal translucency finding.
- name: Type II Transferrin Isoelectric Focusing Pattern
  category: Biochemical
  description: Serum transferrin isoelectric focusing shows a CDG type II profile with increased disialo- and trisialotransferrin, reflecting the terminal sialylation defect rather than a precursor-assembly defect.
  phenotype_term:
    preferred_term: Type II transferrin isoform profile
    term:
      id: HP:0012301
      label: Type II transferrin isoform profile
  notes: The diagnostic biochemical signature. Directly reported in PMID:28619360; the index report (PMID:17331980) describes the same defect at the level of serum transferrin and total serum N-glycans.
  evidence:
  - reference: PMID:28619360
    reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The transferrin isoelectric focusing profiles in the patient showed a CDG type II pattern with increased disialo- and trisialo-transferrin.
    explanation: Directly reports the CDG type II transferrin pattern.
  - reference: PMID:17331980
    reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Analysis of serum transferrin and total serum N-glycans showed normal addition of one sialic acid, but severe deficiency in subsequent sialylation of mostly normal N-glycans.
    explanation: The index report characterises the same serum transferrin sialylation defect that produces the type II pattern.
- name: Developmental regression
  category: Neurological
  description: Loss of acquired psychomotor skills began at six months in the p.Tyr537Ter patient; some subsequent developmental progress was documented.
  phenotype_term:
    preferred_term: Developmental regression
    term:
      id: HP:0002376
      label: Developmental regression
  evidence:
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Although the neonatal period and early infancy were normal, at the age of 6 months, she presented with an acute encephalopathy and loss of psychomotor abilities, hypotonia, alternating esotropia, pseudo-ptosis and mental retardation.
    explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
- name: Encephalopathy
  category: Neurological
  description: Acute episodes were described in the p.Tyr537Ter patient, including during intercurrent illness.
  phenotype_term:
    preferred_term: Encephalopathy
    term:
      id: HP:0001298
      label: Encephalopathy
  evidence:
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Although the neonatal period and early infancy were normal, at the age of 6 months, she presented with an acute encephalopathy and loss of psychomotor abilities, hypotonia, alternating esotropia, pseudo-ptosis and mental retardation.
    explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
- name: Esotropia
  category: Ophthalmologic
  description: Alternating esotropia was present from infancy in the p.Tyr537Ter patient.
  phenotype_term:
    preferred_term: Esotropia
    term:
      id: HP:0000565
      label: Esotropia
  evidence:
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Although the neonatal period and early infancy were normal, at the age of 6 months, she presented with an acute encephalopathy and loss of psychomotor abilities, hypotonia, alternating esotropia, pseudo-ptosis and mental retardation.
    explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/
    reference_title: Congenital Disorders of N-Linked Glycosylation and Multiple Pathway Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Two affected infants with severe developmental delay, hypotonia, seizures, esotropia, failure to thrive, and progressive microcephaly were reported
    explanation: COG8-specific paragraph of the retired GeneReviews overview; supports association, not a frequency estimate.
- name: Ataxia
  category: Neurological
  description: Cerebellar ataxia progressed in the p.Tyr537Ter patient despite little change on interval MRI.
  phenotype_term:
    preferred_term: Ataxia
    term:
      id: HP:0001251
      label: Ataxia
  evidence:
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: From the age of 7, her cerebellar ataxia has worsened.
    explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
- name: Action myoclonus
  category: Neurological
  description: Action myoclonus accompanied the cerebellar syndrome in the p.Tyr537Ter patient.
  phenotype_term:
    preferred_term: Action myoclonus
    term:
      id: HP:0034360
      label: Action myoclonus
  evidence:
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: She later developed a cerebellar syndrome with prominent ataxia and action myoclonus.
    explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
- name: Oculomotor apraxia
  category: Ophthalmologic
  description: Detailed assessment at eight years identified oculomotor apraxia.
  phenotype_term:
    preferred_term: Oculomotor apraxia
    term:
      id: HP:0000657
      label: Oculomotor apraxia
  evidence:
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: A detailed clinical evaluation now revealed an oculomotor apraxia with dysinergia oculocephalica, in addition to the pseudo-ptosis and alternating esotropia; fundoscopy was normal.
    explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
- name: Absent Achilles reflex
  category: Neurological
  description: Absent Achilles reflexes and foot drop suggested lower-limb neuropathy; nerve conduction studies were not performed.
  phenotype_term:
    preferred_term: Absent Achilles reflex
    term:
      id: HP:0003438
      label: Absent Achilles reflex
  evidence:
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: She has symptoms of neuropathy in the lower limbs because she walks with ataxia and foot drop; she has abolished achilles tendon reflexes.
    explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
- name: Foot dorsiflexor weakness
  category: Neurological
  description: Foot drop was reported clinically in the p.Tyr537Ter patient without electrophysiological characterization.
  phenotype_term:
    preferred_term: Foot dorsiflexor weakness
    term:
      id: HP:0009027
      label: Foot dorsiflexor weakness
  evidence:
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: She has symptoms of neuropathy in the lower limbs because she walks with ataxia and foot drop; she has abolished achilles tendon reflexes.
    explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
- name: Brainstem atrophy
  category: Neurological
  description: Slight brainstem atrophy accompanied cerebellar atrophy in the p.Tyr537Ter patient.
  phenotype_term:
    preferred_term: Atrophy/Degeneration affecting the brainstem
    term:
      id: HP:0007366
      label: Atrophy/Degeneration affecting the brainstem
  evidence:
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: At the age of 6 years, brain magnetic resonance imaging (MRI) showed cerebellar atrophy and slight brainstem atrophy
    explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
- name: Short stature
  category: Growth
  description: Short stature was reported in the p.Tyr537Ter patient.
  phenotype_term:
    preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  evidence:
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: The Cog8-defective patient suffers from cerebellar atrophy, mental and motor retardation, hypotonia, growth delay and short stature.
    explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
- name: Abnormality of coagulation
  category: Hematological
  description: Fluctuating coagulation-factor abnormalities and spontaneous hematomas occurred in the p.Tyr537Ter patient; the study also documented reduced protein C and protein S. The cause of each individual factor change was not resolved.
  phenotype_term:
    preferred_term: Abnormality of coagulation
    term:
      id: HP:0001928
      label: Abnormality of coagulation
  evidence:
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: During some other episodes, she presented spontaneous hematomas, coincident with alteration of the coagulation factors and a decrease in the prothrombin time, together with increased levels of transaminases and of creatine kinase.
    explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
- name: Bruising susceptibility
  category: Hematological
  description: Spontaneous hematomas accompanied episodes with abnormal coagulation studies in the p.Tyr537Ter patient.
  phenotype_term:
    preferred_term: Bruising susceptibility
    term:
      id: HP:0000978
      label: Bruising susceptibility
  evidence:
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: During some other episodes, she presented spontaneous hematomas, coincident with alteration of the coagulation factors and a decrease in the prothrombin time, together with increased levels of transaminases and of creatine kinase.
    explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
- name: Elevated creatine kinase
  category: Musculoskeletal
  description: Creatine kinase elevations were reported during some episodes of illness in the p.Tyr537Ter patient.
  phenotype_term:
    preferred_term: Elevated circulating creatine kinase activity
    term:
      id: HP:0003236
      label: Elevated circulating creatine kinase activity
  evidence:
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: During some other episodes, she presented spontaneous hematomas, coincident with alteration of the coagulation factors and a decrease in the prothrombin time, together with increased levels of transaminases and of creatine kinase.
    explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
- name: Recurrent fever
  category: Constitutional
  description: The p.Tyr537Ter patient had a reported PFAPA-like syndrome in infancy. This does not establish a uniform autoinflammatory mechanism across COG8-CDG.
  phenotype_term:
    preferred_term: Recurrent fever
    term:
      id: HP:0001954
      label: Recurrent fever
  evidence:
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: During infancy, she exhibited PFAPA syndrome (periodic fever, aphthous stomatitis, pharyngitis and adenitis)
    explanation: Reported in the p.Tyr537Ter patient; a single case does not establish population frequency.
- name: Reduced protein C activity
  category: Hematological
  description: Protein C deficiency was reported among fluctuating coagulation abnormalities in the p.Tyr537Ter patient. This observation does not establish a separate inherited protein C deficiency disorder.
  phenotype_term:
    preferred_term: Reduced protein C activity
    term:
      id: HP:0005543
      label: Reduced protein C activity
  evidence:
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Because of her occasional coagulation problems, bleeding or thrombosis, and the fluctuation of the coagulation parameters throughout development (protein C and protein S deficiency, decreased prothrombin time and coagulation factors), a wide study for
    explanation: Direct clinical observation in one patient; no population frequency or independent causal mechanism is established.
- name: Reduced protein S activity
  category: Hematological
  description: Protein S deficiency was reported among fluctuating coagulation abnormalities in the p.Tyr537Ter patient. This observation does not establish a separate inherited protein S deficiency disorder.
  phenotype_term:
    preferred_term: Reduced protein S activity
    term:
      id: HP:0004855
      label: Reduced protein S activity
  evidence:
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Because of her occasional coagulation problems, bleeding or thrombosis, and the fluctuation of the coagulation parameters throughout development (protein C and protein S deficiency, decreased prothrombin time and coagulation factors), a wide study for
    explanation: Direct clinical observation in one patient; no population frequency or independent causal mechanism is established.
- name: Sandal gap
  category: Musculoskeletal
  description: A wide first-to-second toe gap was documented in the p.Tyr537Ter patient.
  phenotype_term:
    preferred_term: Sandal gap
    term:
      id: HP:0001852
      label: Sandal gap
  evidence:
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: 'Minor dysmorphic features: small feet, wide space between the first and second toes and clinodactyly of the third and fourth toes can be observed.'
    explanation: Direct clinical observation in one patient; no population frequency or independent causal mechanism is established.
- name: Clinodactyly of the 3rd toe
  category: Musculoskeletal
  description: Third-toe clinodactyly was documented in the p.Tyr537Ter patient.
  phenotype_term:
    preferred_term: Clinodactyly of the 3rd toe
    term:
      id: HP:0008115
      label: Clinodactyly of the 3rd toe
  evidence:
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: 'Minor dysmorphic features: small feet, wide space between the first and second toes and clinodactyly of the third and fourth toes can be observed.'
    explanation: Direct clinical observation in one patient; no population frequency or independent causal mechanism is established.
- name: Clinodactyly of the 4th toe
  category: Musculoskeletal
  description: Fourth-toe clinodactyly was documented in the p.Tyr537Ter patient.
  phenotype_term:
    preferred_term: Clinodactyly of the 4th toe
    term:
      id: HP:0011918
      label: Clinodactyly of the 4th toe
  evidence:
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: 'Minor dysmorphic features: small feet, wide space between the first and second toes and clinodactyly of the third and fourth toes can be observed.'
    explanation: Direct clinical observation in one patient; no population frequency or independent causal mechanism is established.
genetic:
- name: COG8 pathogenic variants
  association: Causal
  relationship_type: CAUSATIVE
  presence: Pathogenic
  gene_term:
    preferred_term: COG8
    term:
      id: hgnc:18623
      label: COG8
  notes: 'Published genotypes include early and late frameshifts, a nonsense allele and splice-altering variants. The 2019 exon 5 hotspot suggestion does not imply that every causal allele lies there: an intron 3 splice donor allele is explicitly documented in the 2007 report.'
  evidence:
  - reference: PMID:17331980
    reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We describe a new Type II congenital disorder of glycosylation (CDG-II) caused by mutations in the conserved oligomeric Golgi (COG) complex gene, COG8.
    explanation: Establishes COG8 as the causal gene.
  - reference: PMID:28619360
    reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'Targeted exome sequencing was performed to screen all CDG type II-related genes, and two novel frameshift mutations were found: c.171dupG (p.Leu58Alafs*29) and c.1656dupC (p.Ala553Argfs*15) in COG8.'
    explanation: Reports two further truncating COG8 alleles in a third patient.
  - reference: PMID:17331980
    reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: The first, IVS3 + 1G > A, altered the conserved splicing site of intron 3, and the second deleted two nucleotides (1687-1688 del TT) in exon 5, truncating the last 47 amino acids.
    explanation: Direct counterexample to a universal exon 5 location claim.
  variants:
  - name: c.1611C>G (p.Tyr537Ter)
    description: A homozygous nonsense change introducing a premature stop codon, leaving a Cog8 subunit that lacks its 76 C-terminal amino acids and so cannot bind Cog1.
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:17220172
      reference_title: A new inborn error of glycosylation due to a Cog8 deficiency reveals a critical role for the Cog1-Cog8 interaction in COG complex formation.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: This leads to a premature stop codon resulting in a truncated Cog8 subunit lacking the 76 C-terminal amino acids.
      explanation: Defines the allele and the precise extent of the C-terminal truncation.
    - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
      reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: We found a nonsense mutation (C to G) at position c.1611 in the ... COG8 ... cDNA, and this was confirmed by the genomic DNA sequence.
      explanation: Original sequence nomenclature in the clinical report.
    variant_type: single nucleotide variant
    genomic_contexts:
    - coding sequence
  - name: Homozygous exon 5 variant creating a new splice site
    description: The 2019 report describes a homozygous exon 5 splice-creating variant with a truncating consequence. The retrieved abstract does not establish the RNA assay or quantify residual protein.
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:30690882
      reference_title: The first case of antenatal presentation in COG8-congenital disorder of glycosylation with a novel splice site mutation and an extended phenotype.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Trio whole exome sequencing revealed a novel homozygous variant in COG8, which creates a new splice site in exon 5 and protein truncation after 12 amino acids downstream to the newly generated splice site.
      explanation: Defines the antenatally ascertained patient's allele.
  - name: IVS3+1G>A
    variant_type: single nucleotide variant
    genomic_contexts:
    - intron
    description: Splice-donor allele reported in trans to a two-nucleotide deletion. The original report uses IVS3+1G>A nomenclature; this location is intron 3, not exon 5.
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:17331980
      reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: The first, IVS3 + 1G > A, altered the conserved splicing site of intron 3, and the second deleted two nucleotides (1687-1688 del TT) in exon 5, truncating the last 47 amino acids.
      explanation: Direct counterexample to a universal exon 5 location claim.
  - name: c.171dupG and c.1656dupC compound-heterozygous genotype
    description: The 2017 patient carried p.Leu58Alafs*29 and p.Ala553Argfs*15, inherited from the respective heterozygous parents. These predicted truncations do not prove complete absence of COG8 protein in this patient.
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:28619360
      reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: 'Targeted exome sequencing was performed to screen all CDG type II-related genes, and two novel frameshift mutations were found: c.171dupG (p.Leu58Alafs*29) and c.1656dupC (p.Ala553Argfs*15) in COG8.'
      explanation: Reports two further truncating COG8 alleles in a third patient.
prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: The 2019 report described its patient as the fourth published case. This is a historical literature count, not a current global census or a measured population prevalence.
  evidence:
  - reference: PMID:30690882
    reference_title: The first case of antenatal presentation in COG8-congenital disorder of glycosylation with a novel splice site mutation and an extended phenotype.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: To date, only three cases of COG8-CDG have been published but none in the antenatal period.
    explanation: Historical case count reported in 2019.
diagnosis:
- name: Serum transferrin isoelectric focusing
  description: Reported COG8-CDG cases show a type II transferrin profile. The pattern directs a broader CDG evaluation but is not specific to COG8, and diagnostic sensitivity cannot be estimated from these case reports.
  evidence:
  - reference: PMID:28619360
    reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The transferrin isoelectric focusing profiles in the patient showed a CDG type II pattern with increased disialo- and trisialo-transferrin.
    explanation: Reports the diagnostic transferrin pattern.
- name: Targeted or trio exome sequencing of CDG type II genes
  description: Molecular identification of biallelic COG8 variants and segregation analysis establish the genetic diagnosis. The 2017 and 2019 reports used targeted and trio exome sequencing. The type II transferrin pattern alone does not identify the responsible gene.
  evidence:
  - reference: PMID:28619360
    reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'Targeted exome sequencing was performed to screen all CDG type II-related genes, and two novel frameshift mutations were found: c.171dupG (p.Leu58Alafs*29) and c.1656dupC (p.Ala553Argfs*15) in COG8.'
    explanation: Targeted exome sequencing established the diagnosis.
  - reference: PMID:30690882
    reference_title: The first case of antenatal presentation in COG8-congenital disorder of glycosylation with a novel splice site mutation and an extended phenotype.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Trio whole exome sequencing revealed a novel homozygous variant in COG8, which creates a new splice site in exon 5 and protein truncation after 12 amino acids downstream to the newly generated splice site.
    explanation: Trio exome sequencing established the antenatal diagnosis.
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/
    reference_title: Congenital Disorders of N-Linked Glycosylation and Multiple Pathway Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: INDIRECT
    snippet: If previous biochemical testing is not diagnostic for or suggestive of a particular CDG, molecular testing approaches most often involve use of a ... multigene panel ... or ... more ... comprehensive ... genomic ... testing
    explanation: Retired group-level diagnostic guidance; the COG8 case reports demonstrate exome-based diagnosis.
- name: Apolipoprotein C-III and serum glycan analysis
  description: In the p.Tyr537Ter patient, abnormal ApoC-III isoelectric focusing and serum O-glycan mass spectrometry demonstrated O-glycosylation involvement. Serum N-glycan changes were relatively subtle despite substantial neurological disease.
  evidence:
  - reference: url:https://oup.silverchair-cdn.com/article-minimal/654283
    reference_title: https://oup.silverchair-cdn.com/article-minimal/654283
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: the abnormal IEF of ApoC-III (data not shown) indicates an O-glycosylation deficiency
    explanation: Additional biochemical characterization in a reported patient.
  - reference: PMID:17220172
    reference_title: A new inborn error of glycosylation due to a Cog8 deficiency reveals a critical role for the Cog1-Cog8 interaction in COG complex formation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Mass spectrometric analysis of the N- and O-glycan structures identified a mild sialylation deficiency.
    explanation: Biochemical characterization does not define overall clinical severity.
treatments:
- name: Nutritional and developmental support
  action_category: THERAPEUTIC
  treatment_term:
    preferred_term: Nutritional and developmental support
    term:
      id: NCIT:C15747
      label: Supportive Care
  description: The retired GeneReviews overview recommends nutritional support for failure to thrive and occupational, physical and speech therapy for developmental delay across N-linked and multiple-pathway CDGs. These are general supportive-care recommendations applicable to the corresponding COG8 manifestations, rather than COG8 intervention-trial results.
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/
    reference_title: Congenital Disorders of N-Linked Glycosylation and Multiple Pathway Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: INDIRECT
    snippet: Some children require placement of a nasogastric tube or gastrostomy tube for nutritional support until oral motor skills improve.
    explanation: Historical group-level nutritional support; does not establish COG8-specific tube-feeding outcomes.
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/
    reference_title: Congenital Disorders of N-Linked Glycosylation and Multiple Pathway Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: INDIRECT
    snippet: Occupational therapy, physical therapy, and speech therapy should be instituted. As the developmental gap widens between children with CDG and their unaffected peers, parents, educators, and therapists need continued counseling and support.
    explanation: General developmental-care recommendation in the retired overview, not a COG8-specific efficacy study.
  target_phenotypes:
  - preferred_term: Failure to thrive
    term:
      id: HP:0001508
      label: Failure to thrive
  - preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
- name: Hepatic and coagulation surveillance
  action_category: MONITORING
  treatment_term:
    preferred_term: Clinical Evaluation
    term:
      id: NCIT:C124351
      label: Clinical Evaluation
  description: The retired group-level overview includes liver-function and coagulation-factor surveillance, with hematology assessment before surgery. This is general CDG guidance for manifestations documented in COG8-CDG; the surveillance interval has not been validated specifically in COG8 patients.
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/
    reference_title: Congenital Disorders of N-Linked Glycosylation and Multiple Pathway Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: INDIRECT
    snippet: Consultation with a hematologist is recommended to document the pro- and anti- clotting factor levels and coagulation status.
    explanation: General coagulation assessment recommendation from the retired CDG overview.
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/
    reference_title: Congenital Disorders of N-Linked Glycosylation and Multiple Pathway Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: INDIRECT
    snippet: Liver function tests; thyroid panel; serum concentrations of the clotting factors protein C, protein S, factor IX, and antithrombin III
    explanation: The source lists these under annual surveillance for the broad CDG group; only hepatic/coagulation monitoring is modeled here.
- name: Genetic counseling and reproductive planning
  action_category: COUNSELING_INFORMATIONAL
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  description: Counseling includes segregation and carrier assessment, conditional recurrence risk and reproductive options. The historical overview states that prenatal and preimplantation testing become possible after identification of familial pathogenic variants. Parental carrier status and the familial variants should be established for recurrence-risk counseling.
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/
    reference_title: Congenital Disorders of N-Linked Glycosylation and Multiple Pathway Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: INDIRECT
    snippet: Once the ... pathogenic variant ... (s) have been identified in the family, ... prenatal testing ... for a pregnancy at increased risk and ... preimplantation genetic testing ... for a ... congenital ... disorder of N-linked glycosylation or multiple pathway are possible.
    explanation: General molecularly defined CDG counseling, applicable once familial COG8 variants are established.
- name: Medication precautions with hepatic involvement
  action_category: COUNSELING_INFORMATIONAL
  treatment_term:
    preferred_term: Counseling
    term:
      id: NCIT:C61547
      label: Counseling
  description: The retired overview advises caution with acetaminophen and other hepatically metabolized agents. This is historical general CDG guidance, not evidence that all such agents are contraindicated in COG8-CDG; medication decisions require individual hepatic assessment.
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/
    reference_title: Congenital Disorders of N-Linked Glycosylation and Multiple Pathway Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: INDIRECT
    snippet: Acetominophen and other agents metabolized by the liver should be used with caution.
    explanation: Historical general medication precaution; the source spells acetaminophen as acetominophen. It does not report a COG8-specific adverse-drug study.
- name: Ophthalmologic assessment and strabismus care
  description: The retired general CDG GeneReviews chapter recommends early ophthalmologic assessment and individualized vision-preserving treatment for strabismus. This is historical group-level supportive guidance, not a COG8-specific treatment trial.
  treatment_term:
    preferred_term: Strabismus supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
  action_category: THERAPEUTIC
  target_phenotypes:
  - preferred_term: Esotropia
    term:
      id: HP:0000565
      label: Esotropia
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/
    reference_title: Congenital Disorders of N-Linked Glycosylation and Multiple Pathway Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: INDIRECT
    snippet: Consultation with a pediatric ophthalmologist early in life is important so that potential eye abnormalities can be diagnosed and therapies that preserve vision (glasses, patching, or surgery) can be instituted as needed.
    explanation: Historical general CDG guidance relevant to the reported esotropia.
discussions:
- discussion_id: cog8_proteoglycan_gag_in_patient_tissue
  kind: KNOWLEDGE_GAP
  prompt: Does the reduced glycosaminoglycan modification of proteoglycans seen in COG-subunit knock-out cell lines occur in COG8-CDG patient tissue, and does it contribute to the skeletal and connective-tissue features?
  attaches_to:
  - experimental_models#COG8-knockout HEK293T proteoglycan model
  rationale: Engineered COG8-knockout HEK293T cells have altered proteoglycan synthesis readouts, but their contribution to human COG8-CDG manifestations remains untested in the cited studies. Altered turnover was proposed rather than kinetically measured.
  evidence:
  - reference: PMID:34053170
    reference_title: Proteoglycan synthesis in conserved oligomeric Golgi subunit deficient HEK293T cells is affected differently, depending on the lacking subunit.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: In light of the important roles PGs play in animal development, the effects KO of individual COG subunits have on GAG synthesis could explain the variable severity of COG associated CDGs.
    explanation: The authors state the hypothesis this gap would test, and frame it as a possible rather than established explanation.
- discussion_id: cog8_severity_range_with_clustered_truncating_alleles
  kind: KNOWLEDGE_GAP
  prompt: What determines the clinical severity range in COG8-CDG, and how do residual protein, complex assembly and tissue context contribute?
  attaches_to:
  - pathophysiology#Abnormal N-glycan sialylation
  - genetic#COG8 pathogenic variants
  rationale: Residual truncated protein and biochemical sialylation defects differ between patient lines. A biochemically mild sialylation defect can accompany substantial neurological disease. The small case series cannot establish a genotype-severity model; the reported exon 5 clustering is not universal.
  evidence:
  - reference: PMID:28619360
    reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Compared with the previous two reported cases, our patient showed relatively mild psychomotor retardation without a seizure history.
    explanation: Documents the severity difference between reported patients that this gap concerns.
  - reference: PMID:17220172
    reference_title: A new inborn error of glycosylation due to a Cog8 deficiency reveals a critical role for the Cog1-Cog8 interaction in COG complex formation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Mass spectrometric analysis of the N- and O-glycan structures identified a mild sialylation deficiency.
    explanation: Biochemically mild result does not imply absence of major neurological disability.
- discussion_id: cog8_glycan_to_organ_mechanisms
  kind: KNOWLEDGE_GAP
  prompt: Which COG8-dependent trafficking and glycosylation defects cause the specific neurological, hepatic and coagulation manifestations?
  attaches_to:
  - pathophysiology#Abnormal N-glycan sialylation
  - pathophysiology#Abnormal O-glycan sialylation
  rationale: Cellular complementation establishes COG8 dependence for trafficking and glycan readouts, but specific substrate-to-organ causal chains have not been established in these studies. Clinical edges therefore retain unknown intermediates.
  evidence:
  - reference: PMID:23865579
    reference_title: Deficiency of the Cog8 subunit in normal and CDG-derived cells impairs the assembly of the COG and Golgi SNARE complexes.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: BACKGROUND
    directness: DIRECT
    snippet: Yet, the connection between COG function, its complex integrity and CDG pathology remains largely unknown.
    explanation: The mechanistic study states the unresolved connection to clinical pathology.
experimental_models:
- name: COG8-deficient CDG patient fibroblasts with lentiviral complementation
  experimental_model_type: PRIMARY_CELL_CULTURE
  description: Patient fibroblasts from the Kranz et al. case had undetectable COG8, abnormal subunit localization, hyposialylation and delayed BFA response. Lentiviral wild-type COG8 corrected these cellular readouts. Complementation supports a causal contribution of COG8 dysfunction but does not establish clinical treatment efficacy.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  modeled_mechanisms:
  - target: Reduced COG8 protein abundance
    relationship: RECAPITULATES
    fidelity: HIGH
    description: The patient-derived line directly models the undetectable COG8 protein reported for this genotype.
    limitations: Fibroblasts are not an affected tissue in the neurological phenotype, and a single patient's cells cannot represent the allelic spectrum.
    evidence:
    - reference: PMID:17331980
      reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: Patient fibroblasts completely lacked COG8 protein and had reduced levels and/or mislocalization of several other COG proteins.
      explanation: Undetectable COG8 protein in this patient fibroblast line.
    model_scale: CELLULAR
    divergences:
    - divergence_type: BOUNDARY_OMISSION
      materiality: QUALIFYING
      description: Cultured cells do not include the neural, hepatic and systemic interactions needed to explain the clinical phenotype.
  - target: Abnormal N-glycan sialylation
    relationship: RESCUES
    model_scale: CELLULAR
    limitations: Correction in cultured fibroblasts does not establish rescue of neurological or other clinical outcomes.
    divergences:
    - divergence_type: BOUNDARY_OMISSION
      materiality: QUALIFYING
      description: Cultured cells do not include the neural, hepatic and systemic interactions needed to explain the clinical phenotype.
    readouts:
    - name: Restored N-glycan sialylation
      target: Abnormal N-glycan sialylation
      direction: RESTORED
      interpretation: Wild-type COG8 complementation restores this cellular readout, supporting COG8 dependence without establishing clinical treatment benefit.
      evidence:
      - reference: PMID:17331980
        reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: Lentiviral-mediated complementation with normal COG8 corrected mislocalization of other COG proteins, normalized sialylation and restored normal BFA-induced Golgi disruption.
        explanation: Reports the rescue of all three cellular readouts.
    evidence:
    - reference: PMID:17331980
      reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: Lentiviral-mediated complementation with normal COG8 corrected mislocalization of other COG proteins, normalized sialylation and restored normal BFA-induced Golgi disruption.
      explanation: Reports the rescue of all three cellular readouts.
  - target: Abnormal O-glycan sialylation
    relationship: RESCUES
    model_scale: CELLULAR
    limitations: Correction in cultured fibroblasts does not establish rescue of neurological or other clinical outcomes.
    divergences:
    - divergence_type: BOUNDARY_OMISSION
      materiality: QUALIFYING
      description: Cultured cells do not include the neural, hepatic and systemic interactions needed to explain the clinical phenotype.
    readouts:
    - name: Restored O-glycan sialylation
      target: Abnormal O-glycan sialylation
      direction: RESTORED
      interpretation: Wild-type COG8 complementation restores this cellular readout, supporting COG8 dependence without establishing clinical treatment benefit.
      evidence:
      - reference: PMID:17331980
        reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: Lentiviral-mediated complementation with normal COG8 corrected mislocalization of other COG proteins, normalized sialylation and restored normal BFA-induced Golgi disruption.
        explanation: Reports the rescue of all three cellular readouts.
    evidence:
    - reference: PMID:17331980
      reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: Lentiviral-mediated complementation with normal COG8 corrected mislocalization of other COG proteins, normalized sialylation and restored normal BFA-induced Golgi disruption.
      explanation: Reports the rescue of all three cellular readouts.
  - target: Delayed Golgi-to-ER retrograde transport
    relationship: RESCUES
    model_scale: CELLULAR
    limitations: Correction in cultured fibroblasts does not establish rescue of neurological or other clinical outcomes.
    divergences:
    - divergence_type: BOUNDARY_OMISSION
      materiality: QUALIFYING
      description: Cultured cells do not include the neural, hepatic and systemic interactions needed to explain the clinical phenotype.
    readouts:
    - name: Restored brefeldin A-induced Golgi redistribution
      target: Delayed Golgi-to-ER retrograde transport
      direction: RESTORED
      interpretation: Wild-type COG8 complementation restores this cellular readout, supporting COG8 dependence without establishing clinical treatment benefit.
      evidence:
      - reference: PMID:17331980
        reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: Lentiviral-mediated complementation with normal COG8 corrected mislocalization of other COG proteins, normalized sialylation and restored normal BFA-induced Golgi disruption.
        explanation: Reports the rescue of all three cellular readouts.
    evidence:
    - reference: PMID:17331980
      reference_title: COG8 deficiency causes new congenital disorder of glycosylation type IIh.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: Lentiviral-mediated complementation with normal COG8 corrected mislocalization of other COG proteins, normalized sialylation and restored normal BFA-induced Golgi disruption.
      explanation: Reports the rescue of all three cellular readouts.
- name: COG8 shRNA knockdown HeLa cells
  experimental_model_type: CELL_LINE
  description: COG8 shRNA depletion in HeLa cells was studied using both transient and stable lines. The cells showed altered Golgi organization, impaired SNARE assembly and endosome-to-TGN transport; the system differs from the patient genotypes and cellular context.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  modeled_mechanisms:
  - target: Impaired Golgi SNARE complex assembly
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: Reduced SNARE complex assembly is also observed in the tested patient fibroblasts.
    limitations: 'HeLa depletion does not reproduce all patient-cell effects: GS15 abundance increased in depleted HeLa cells but decreased in patient fibroblasts; VAMP4 abundance was unchanged in HeLa cells but reduced in patient cells.'
    evidence:
    - reference: PMID:23865579
      reference_title: Deficiency of the Cog8 subunit in normal and CDG-derived cells impairs the assembly of the COG and Golgi SNARE complexes.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: By detailed analysis of Cog8 deficiency in either HeLa cells or CDG-derived fibroblasts, we show that Cog8 is required for the assembly of both the COG complex and the Golgi Stx5-GS28-Ykt6-GS15 and Stx6-Stx16-Vti1a-VAMP4 SNARE complexes.
      explanation: Establishes the knockdown line as informative for the tethering and SNARE-assembly node.
    model_scale: CELLULAR
    divergences:
    - divergence_type: BOUNDARY_OMISSION
      materiality: QUALIFYING
      description: Cultured cells do not include the neural, hepatic and systemic interactions needed to explain the clinical phenotype.
  findings:
  - statement: Dilated Golgi cisternae and accumulated perigolgi vesicles were observed by electron microscopy; failed tethering or fusion was an interpretation, not a directly measured event.
    evidence:
    - reference: PMID:23865579
      reference_title: Deficiency of the Cog8 subunit in normal and CDG-derived cells impairs the assembly of the COG and Golgi SNARE complexes.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: Electron microscopy analysis further exposed a dilation of Golgi cisternae and accumulation of vesicles in the vicinity of the Golgi (Figure 1B), which possibly represent vesicles that failed to fuse with the Golgi membranes.
      explanation: Morphology supports a trafficking defect without identifying the precise failed step.
- name: COG8 siRNA-depleted HeLa cells
  experimental_model_type: CELL_LINE
  description: HeLa COG8 knockdown models showed altered Golgi enzyme localization and lectin readouts, but total cellular N-glycan mass spectrometry did not reproduce patient serum hyposialylation.
  modeled_mechanisms:
  - target: Abnormal N-glycan sialylation
    relationship: FAILS_TO_RECAPITULATE
    model_scale: CELLULAR
    limitations: Acute knockdown in transformed cells and total-cell glycans differ from patient genotypes and serum proteins.
    evidence:
    - reference: PMID:21421995
      reference_title: Conserved oligomeric Golgi complex specifically regulates the maintenance of Golgi glycosylation machinery.
      supports: REFUTE
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: Surprisingly, the data also show a minor increase in sialylation in the N-glycans of COG6- and COG8-deficient cells.
      explanation: Total-cell HeLa N-glycans differ from patient serum findings; the model does not reproduce this readout.
    divergences:
    - divergence_type: BOUNDARY_OMISSION
      materiality: QUALIFYING
      description: Cultured cells do not include the neural, hepatic and systemic interactions needed to explain the clinical phenotype.
    - divergence_type: PROXY_QUANTITY
      materiality: QUALIFYING
      description: The mass-spectrometry measurement is total cellular N-glycans, whereas the clinical comparison is serum glycoprotein N-glycans. Their measured sialylation changes have opposite directions.
  evidence:
  - reference: PMID:21421995
    reference_title: Conserved oligomeric Golgi complex specifically regulates the maintenance of Golgi glycosylation machinery.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: In all analyzed COG KD cells, MGAT1, MAN2A1 and ST6GAL1 proteins were found in multiple vesicle-like structures, as well as in large fragmented Golgi mini-stacks that were positive for the Golgi matrix protein GM130.
    explanation: The tested panel included COG8-depleted HeLa cells.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
- name: COG8-knockout HEK293T proteoglycan model
  experimental_model_type: CELL_LINE
  description: CRISPR/Cas9 COG8-knockout HEK293T cells have reduced sulfate incorporation into proteoglycans, preserved chain lengths on secreted proteoglycans, longer cell-associated GAG chains and preserved surface 10E4 antibody recognition. These findings do not establish a patient-tissue proteoglycan defect or clinical severity mechanism.
  modeled_mechanisms:
  - target: Biallelic COG8 dysfunction
    relationship: PERTURBS
    model_scale: CELLULAR
    limitations: Complete engineered knockout differs from individual patient alleles; no clinical skeletal phenotype is reproduced.
    evidence:
    - reference: PMID:34053170
      reference_title: Proteoglycan synthesis in conserved oligomeric Golgi subunit deficient HEK293T cells is affected differently, depending on the lacking subunit.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: We here show that glycosaminoglycan (GAG) modification of PGs is significantly reduced, regardless which COG subunit that is missing in HEK293T cells.
      explanation: KO model readout, not a measured patient phenotype.
    divergences:
    - divergence_type: BOUNDARY_OMISSION
      materiality: QUALIFYING
      description: Cultured cells do not include the neural, hepatic and systemic interactions needed to explain the clinical phenotype.
  findings:
  - statement: Secreted proteoglycan GAG chain lengths were preserved in COG8-knockout cells.
    evidence:
    - reference: PMID:34053170
      reference_title: Proteoglycan synthesis in conserved oligomeric Golgi subunit deficient HEK293T cells is affected differently, depending on the lacking subunit.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: COG1 and COG8 (figure 4, panels C and J) deficient cells displayed GAG chains of similar length to the wild type cells
      explanation: Secreted-chain finding distinguishes COG8 from several other COG subunit knockouts.
  - statement: Surface heparan sulfate 10E4 recognition was preserved despite reduced overall proteoglycan synthesis.
    evidence:
    - reference: PMID:34053170
      reference_title: Proteoglycan synthesis in conserved oligomeric Golgi subunit deficient HEK293T cells is affected differently, depending on the lacking subunit.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: A surprising finding was that, both COG1 and COG8 deficient cells were recognized to the same extent as wild type cells
      explanation: The 10E4 flow-cytometry result does not measure all heparan sulfate functions.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
notes: COG8-CDG, CDG-IIh and CDG-II/COG8 name the same recessive disorder. The available case reports define a variable spectrum, not population phenotype frequencies. General care and reproductive guidance cited from the retired GeneReviews overview is historical and group-level; cellular rescue experiments are not clinical gene-therapy evidence.
datasets: []
histopathology:
- name: Interface hepatitis with mild lobular activity
  description: Liver biopsy in the 2017 Korean patient showed interface hepatitis with mild lobular activity. This single observation is not a COG8-specific diagnostic pattern.
  diagnostic: false
  evidence:
  - reference: PMID:28619360
    reference_title: 'Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: A liver biopsy of the patient showed only interface hepatitis with mild lobular activity, and brain magnetic resonance imaging revealed cerebellar atrophy.
    explanation: Biopsy morphology in one Korean patient; this does not establish a specific inflammatory mechanism or a population frequency.
    quote_role: PRIMARY_RESULT
    directness: DIRECT

📚

References & Deep Research

References

11

PMID:17220172

A new inborn error of glycosylation due to a Cog8 deficiency reveals a critical role for the Cog1-Cog8 interaction in COG complex formation.

No top-level findings curated for this source.

PMID:17331980

COG8 deficiency causes new congenital disorder of glycosylation type IIh.

No top-level findings curated for this source.

PMID:17904886

Deficiencies in subunits of the Conserved Oligomeric Golgi (COG) complex define a novel group of Congenital Disorders of Glycosylation.

No top-level findings curated for this source.

PMID:21421995

Conserved oligomeric Golgi complex specifically regulates the maintenance of Golgi glycosylation machinery.

No top-level findings curated for this source.

PMID:23865579

Deficiency of the Cog8 subunit in normal and CDG-derived cells impairs the assembly of the COG and Golgi SNARE complexes.

No top-level findings curated for this source.

PMID:28619360

Further delineation of COG8-CDG: A case with novel compound heterozygous mutations diagnosed by targeted exome sequencing.

No top-level findings curated for this source.

PMID:30690882

The first case of antenatal presentation in COG8-congenital disorder of glycosylation with a novel splice site mutation and an extended phenotype.

No top-level findings curated for this source.

PMID:34053170

Proteoglycan synthesis in conserved oligomeric Golgi subunit deficient HEK293T cells is affected differently, depending on the lacking subunit.

No top-level findings curated for this source.

url:https://oup.silverchair-cdn.com/article-minimal/654283

https://oup.silverchair-cdn.com/article-minimal/654283

1 finding

Publisher-hosted full text of Foulquier et al., A new inborn error of glycosylation due to a Cog8 deficiency reveals a critical role for the Cog1-Cog8 interaction in COG complex formation (Human Molecular Genetics 16:717-730, 2007; PMID:17220172; DOI:10.1093/hmg/ddl476).

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1332/

Congenital Disorders of N-Linked Glycosylation and Multiple Pathway Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY - GeneReviews® - NCBI Bookshelf

No top-level findings curated for this source.

PMID:20301507

Congenital Disorders of N-Linked Glycosylation and Multiple Pathway Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY.

No top-level findings curated for this source.

COG8-congenital disorder of glycosylation

Ask OpenScientist

OpenScientist Report

Inheritance

Discussions and Knowledge Gaps

Pathophysiology

Histopathology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Diagnosis

Prevalence

Experimental Models

Source YAML

References & Deep Research

References